小开

最佳答案

I really recommend using some sort of library, but you asked for it, you get it:

var p = document.querySelector('p'); // element to make resizable


p.addEventListener('click', function init() {
p.removeEventListener('click', init, false);
p.className = p.className + ' resizable';
var resizer = document.createElement('div');
resizer.className = 'resizer';
p.appendChild(resizer);
resizer.addEventListener('mousedown', initDrag, false);
}, false);


var startX, startY, startWidth, startHeight;


function initDrag(e) {
startX = e.clientX;
startY = e.clientY;
startWidth = parseInt(document.defaultView.getComputedStyle(p).width, 10);
startHeight = parseInt(document.defaultView.getComputedStyle(p).height, 10);
document.documentElement.addEventListener('mousemove', doDrag, false);
document.documentElement.addEventListener('mouseup', stopDrag, false);
}


function doDrag(e) {
p.style.width = (startWidth + e.clientX - startX) + 'px';
p.style.height = (startHeight + e.clientY - startY) + 'px';
}


function stopDrag(e) {
document.documentElement.removeEventListener('mousemove', doDrag, false);
document.documentElement.removeEventListener('mouseup', stopDrag, false);
}

Demo

Remember that this may not run in all browsers (tested only in Firefox, definitely not working in IE <9).

小开

what about a pure css3 solution?

div {
resize: both;
overflow: auto;
}

MDN Web Docs

W3Schools example

Browser support

小开

See my cross browser compatible resizer.

    <!doctype html>
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<title>resizer</title>
<meta name="author" content="Andrej Hristoliubov anhr@mail.ru">
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<script type="text/javascript" src="https://rawgit.com/anhr/resizer/master/Common.js"></script>
<script type="text/javascript" src="https://rawgit.com/anhr/resizer/master/resizer.js"></script>
<style>
.element {
border: 1px solid #999999;
border-radius: 4px;
margin: 5px;
padding: 5px;
}
</style>
<script type="text/javascript">
function onresize() {
var element1 = document.getElementById("element1");
var element2 = document.getElementById("element2");
var element3 = document.getElementById("element3");
var ResizerY = document.getElementById("resizerY");
ResizerY.style.top = element3.offsetTop - 15 + "px";
var topElements = document.getElementById("topElements");
topElements.style.height = ResizerY.offsetTop - 20 + "px";
var height = topElements.clientHeight - 32;
if (height < 0)
height = 0;
height += 'px';
element1.style.height = height;
element2.style.height = height;
}
function resizeX(x) {
//consoleLog("mousemove(X = " + e.pageX + ")");
var element2 = document.getElementById("element2");
element2.style.width =
element2.parentElement.clientWidth
+ document.getElementById('rezizeArea').offsetLeft
- x
+ 'px';
}
function resizeY(y) {
//consoleLog("mousemove(Y = " + e.pageY + ")");
var element3 = document.getElementById("element3");
var height =
element3.parentElement.clientHeight
+ document.getElementById('rezizeArea').offsetTop
- y
;
//consoleLog("mousemove(Y = " + e.pageY + ") height = " + height + " element3.parentElement.clientHeight = " + element3.parentElement.clientHeight);
if ((height + 100) > element3.parentElement.clientHeight)
return;//Limit of the height of the elemtnt 3
element3.style.height = height + 'px';
onresize();
}
var emailSubject = "Resizer example error";
</script>
</head>
<body>
<div id='Message'></div>
<h1>Resizer</h1>
<p>Please see example of resizing of the HTML element by mouse dragging.</p>
<ul>
<li>Drag the red rectangle if you want to change the width of the Element 1 and Element 2</li>
<li>Drag the green rectangle if you want to change the height of the Element 1 Element 2 and Element 3</li>
<li>Drag the small blue square at the left bottom of the Element 2, if you want to resize of the Element 1 Element 2 and Element 3</li>
</ul>
<div id="rezizeArea" style="width:1000px; height:250px; overflow:auto; position: relative;" class="element">
<div id="topElements" class="element" style="overflow:auto; position:absolute; left: 0; top: 0; right:0;">
<div id="element2" class="element" style="width: 30%; height:10px; float: right; position: relative;">
Element 2
<div id="resizerXY" style="width: 10px; height: 10px; background: blue; position:absolute; left: 0; bottom: 0;"></div>
<script type="text/javascript">
resizerXY("resizerXY", function (e) {
resizeX(e.pageX + 10);
resizeY(e.pageY + 50);
});
</script>
</div>
<div id="resizerX" style="width: 10px; height:100%; background: red; float: right;"></div>
<script type="text/javascript">
resizerX("resizerX", function (e) {
resizeX(e.pageX + 25);
});
</script>
<div id="element1" class="element" style="height:10px; overflow:auto;">Element 1</div>
</div>
<div id="resizerY" style="height:10px; position:absolute; left: 0; right:0; background: green;"></div>
<script type="text/javascript">
resizerY("resizerY", function (e) {
resizeY(e.pageY + 25);
});
</script>
<div id="element3" class="element" style="height:100px; position:absolute; left: 0; bottom: 0; right:0;">Element 3</div>
</div>
<script type="text/javascript">
onresize();
</script>
</body>
</html>

Also see my example of resizer

小开

Is simple:

Example:https://jsfiddle.net/RainStudios/mw786v1w/

var element = document.getElementById('element');
//create box in bottom-left
var resizer = document.createElement('div');
resizer.style.width = '10px';
resizer.style.height = '10px';
resizer.style.background = 'red';
resizer.style.position = 'absolute';
resizer.style.right = 0;
resizer.style.bottom = 0;
resizer.style.cursor = 'se-resize';
//Append Child to Element
element.appendChild(resizer);
//box function onmousemove
resizer.addEventListener('mousedown', initResize, false);


//Window funtion mousemove & mouseup
function initResize(e) {
window.addEventListener('mousemove', Resize, false);
window.addEventListener('mouseup', stopResize, false);
}
//resize the element
function Resize(e) {
element.style.width = (e.clientX - element.offsetLeft) + 'px';
element.style.height = (e.clientY - element.offsetTop) + 'px';
}
//on mouseup remove windows functions mousemove & mouseup
function stopResize(e) {
window.removeEventListener('mousemove', Resize, false);
window.removeEventListener('mouseup', stopResize, false);
}

小开

I just created a CodePen that shows how this can be done pretty easily using ES6.

http://codepen.io/travist/pen/GWRBQV

Basically, here is the class that does this.

let getPropertyValue = function(style, prop) {
let value = style.getPropertyValue(prop);
value = value ? value.replace(/[^0-9.]/g, '') : '0';
return parseFloat(value);
}


let getElementRect = function(element) {
let style = window.getComputedStyle(element, null);
return {
x: getPropertyValue(style, 'left'),
y: getPropertyValue(style, 'top'),
width: getPropertyValue(style, 'width'),
height: getPropertyValue(style, 'height')
}
}


class Resizer {
constructor(wrapper, element, options) {
this.wrapper = wrapper;
this.element = element;
this.options = options;
this.offsetX = 0;
this.offsetY = 0;
this.handle = document.createElement('div');
this.handle.setAttribute('class', 'drag-resize-handlers');
this.handle.setAttribute('data-direction', 'br');
this.wrapper.appendChild(this.handle);
this.wrapper.style.top = this.element.style.top;
this.wrapper.style.left = this.element.style.left;
this.wrapper.style.width = this.element.style.width;
this.wrapper.style.height = this.element.style.height;
this.element.style.position = 'relative';
this.element.style.top = 0;
this.element.style.left = 0;
this.onResize = this.resizeHandler.bind(this);
this.onStop = this.stopResize.bind(this);
this.handle.addEventListener('mousedown', this.initResize.bind(this));
}


initResize(event) {
this.stopResize(event, true);
this.handle.addEventListener('mousemove', this.onResize);
this.handle.addEventListener('mouseup', this.onStop);
}


resizeHandler(event) {
this.offsetX = event.clientX - (this.wrapper.offsetLeft + this.handle.offsetLeft);
this.offsetY = event.clientY - (this.wrapper.offsetTop + this.handle.offsetTop);
let wrapperRect = getElementRect(this.wrapper);
let elementRect = getElementRect(this.element);
this.wrapper.style.width = (wrapperRect.width + this.offsetX) + 'px';
this.wrapper.style.height = (wrapperRect.height + this.offsetY) + 'px';
this.element.style.width = (elementRect.width + this.offsetX) + 'px';
this.element.style.height = (elementRect.height + this.offsetY) + 'px';
}


stopResize(event, nocb) {
this.handle.removeEventListener('mousemove', this.onResize);
this.handle.removeEventListener('mouseup', this.onStop);
}
}


class Dragger {
constructor(wrapper, element, options) {
this.wrapper = wrapper;
this.options = options;
this.element = element;
this.element.draggable = true;
this.element.setAttribute('draggable', true);
this.element.addEventListener('dragstart', this.dragStart.bind(this));
}


dragStart(event) {
let wrapperRect = getElementRect(this.wrapper);
var x = wrapperRect.x - parseFloat(event.clientX);
var y = wrapperRect.y - parseFloat(event.clientY);
event.dataTransfer.setData("text/plain", this.element.id + ',' + x + ',' + y);
}


dragStop(event, prevX, prevY) {
var posX = parseFloat(event.clientX) + prevX;
var posY = parseFloat(event.clientY) + prevY;
this.wrapper.style.left = posX + 'px';
this.wrapper.style.top = posY + 'px';
}
}


class DragResize {
constructor(element, options) {
options = options || {};
this.wrapper = document.createElement('div');
this.wrapper.setAttribute('class', 'tooltip drag-resize');
if (element.parentNode) {
element.parentNode.insertBefore(this.wrapper, element);
}
this.wrapper.appendChild(element);
element.resizer = new Resizer(this.wrapper, element, options);
element.dragger = new Dragger(this.wrapper, element, options);
}
}


document.body.addEventListener('dragover', function (event) {
event.preventDefault();
return false;
});


document.body.addEventListener('drop', function (event) {
event.preventDefault();
var dropData = event.dataTransfer.getData("text/plain").split(',');
var element = document.getElementById(dropData[0]);
element.dragger.dragStop(event, parseFloat(dropData[1]), parseFloat(dropData[2]));
return false;
});

小开

I have created a function that recieve an id of an html element and adds a border to it's right side the function is general and just recieves an id so you can copy it as it is and it will work

var myoffset;
function resizeE(elem){
var borderDiv = document.createElement("div");
borderDiv.className = "border";
borderDiv.addEventListener("mousedown",myresize = function myrsize(e) {
myoffset = e.clientX - (document.getElementById(elem).offsetLeft + parseInt(window.getComputedStyle(document.getElementById(elem)).getPropertyValue("width")));
window.addEventListener("mouseup",mouseUp);
document.addEventListener("mousemove",mouseMove = function mousMove(e) {
document.getElementById(elem).style.width = `${e.clientX -  myoffset - document.getElementById(elem).offsetLeft}px`;
});
});
document.getElementById(elem).appendChild(borderDiv);
}


function mouseUp() {
document.removeEventListener("mousemove", mouseMove);
window.removeEventListener("mouseup",mouseUp);
}


function load()
{
resizeE("resizeableDiv");
resizeE("anotherresizeableDiv");
resizeE("anotherresizeableDiv1");
}

.border {


position: absolute;
cursor: e-resize;
width: 9px;
right: -5px;
top: 0;
height: 100%;
}


#resizeableDiv {
width: 30vw;
height: 30vh;
background-color: #84f4c6;
position: relative;
}
#anotherresizeableDiv {
width: 30vw;
height: 30vh;
background-color: #9394f4;
position: relative;
}
#anotherresizeableDiv1 {
width: 30vw;
height: 30vh;
background-color: #43f4f4;
position: relative;
}
#anotherresizeableDiv1 .border{
background-color: black;
}
#anotherresizeableDiv .border{
width: 30px;
right: -200px;
background-color: green;
}

<body onload="load()">


<div id="resizeableDiv">change my size with the east border</div>
<div id="anotherresizeableDiv1">with visible border</div>
</body>
<div id="anotherresizeableDiv">with editted outside border</div>
</body>

resizeE("resizeableDiv"); //this calls a function that does the magic to the id inserted

小开

var resizeHandle = document.getElementById('resizable');
var box = document.getElementById('resize');
resizeHandle.addEventListener('mousedown', initialiseResize, false);


function initialiseResize(e) {
window.addEventListener('mousemove', startResizing, false);
window.addEventListener('mouseup', stopResizing, false);
}


function stopResizing(e) {
window.removeEventListener('mousemove', startResizing, false);
window.removeEventListener('mouseup', stopResizing, false);
}


function startResizing(e) {
box.style.width = (e.clientX) + 'px';
box.style.height = (e.clientY) + 'px';
}


function startResizing(e) {
box.style.width = (e.clientX - box.offsetLeft) + 'px';
box.style.height = (e.clientY - box.offsetTop) + 'px';
}

#resize {
position: relative;
width: 130px;
height: 130px;
border: 2px solid blue;
color: white;
}


#resizable {
background-color: white;
width: 10px;
height: 10px;
cursor: se-resize;
position: absolute;
right: 0;
bottom: 0;
}

<div id="resize">


<div id="resizable">
</div>

小开

There are very good examples here to start trying with, but all of them are based on adding some extra or external element like a "div" as a reference element to drag it, and calculate the new dimensions or position of the original element.

Here's an example that doesn't use any extra elements. We could add borders, padding or margin without affecting its operation. In this example we have not added color, nor any visual reference to the borders nor to the lower right corner as a clue where you can enlarge or reduce dimensions, but using the cursor around the resizable elements the clues appears!

let resizerForCenter = new Resizer('center')
resizerForCenter.initResizer()

See it in action with CodeSandbox:

In this example we use ES6, and a module that exports a class called Resizer. An example is worth a thousand words:

Or with the code snippet:

const html = document.querySelector('html')


class Resizer {
constructor(elemId) {
this._elem = document.getElementById(elemId)
/**
* Stored binded context handlers for method passed to eventListeners!
*
* See: https://stackoverflow.com/questions/9720927/removing-event-listeners-as-class-prototype-functions
*/
this._checkBorderHandler	= this._checkBorder.bind(this)
this._doResizeHandler		= this._doResize.bind(this)
this._initResizerHandler	= this.initResizer.bind(this)
this._onResizeHandler		= this._onResize.bind(this)
}


initResizer() {
this.stopResizer()
this._beginResizer()
}


_beginResizer() {
this._elem.addEventListener('mousemove', this._checkBorderHandler, false)
}


stopResizer() {
html.style.cursor	= 'default'
this._elem.style.cursor = 'default'
		

window.removeEventListener('mousemove', this._doResizeHandler, false)
window.removeEventListener('mouseup', this._initResizerHandler, false)


this._elem.removeEventListener('mousedown', this._onResizeHandler, false)
this._elem.removeEventListener('mousemove', this._checkBorderHandler, false)
}


_doResize(e) {
let elem = this._elem


let boxSizing = getComputedStyle(elem).boxSizing
let borderRight = 0
let borderLeft = 0
let borderTop = 0
let borderBottom = 0


let paddingRight = 0
let paddingLeft = 0
let paddingTop = 0
let paddingBottom = 0


switch (boxSizing) {
case 'content-box':
paddingRight = parseInt(getComputedStyle(elem).paddingRight)
paddingLeft = parseInt(getComputedStyle(elem).paddingLeft)
paddingTop = parseInt(getComputedStyle(elem).paddingTop)
paddingBottom = parseInt(getComputedStyle(elem).paddingBottom)
break
case 'border-box':
borderRight = parseInt(getComputedStyle(elem).borderRight)
borderLeft = parseInt(getComputedStyle(elem).borderLeft)
borderTop = parseInt(getComputedStyle(elem).borderTop)
borderBottom = parseInt(getComputedStyle(elem).borderBottom)
break
default: break
}


let horizontalAdjustment	= (paddingRight + paddingLeft) - (borderRight + borderLeft)
let verticalAdjustment		= (paddingTop + paddingBottom) - (borderTop + borderBottom)


let newWidth	= elem.clientWidth  + e.movementX - horizontalAdjustment + 'px'
let newHeight	= elem.clientHeight + e.movementY - verticalAdjustment   + 'px'
		

let cursorType = getComputedStyle(elem).cursor
switch (cursorType) {
case 'all-scroll':
elem.style.width = newWidth
elem.style.height = newHeight
break
case 'col-resize':
elem.style.width = newWidth
break
case 'row-resize':
elem.style.height = newHeight
break
default: break
}
}


_onResize(e) {
// On resizing state!
let elem = e.target
let newCursorType = undefined
let cursorType = getComputedStyle(elem).cursor
switch (cursorType) {
case 'nwse-resize':
newCursorType = 'all-scroll'
break
case 'ew-resize':
newCursorType = 'col-resize'
break
case 'ns-resize':
newCursorType = 'row-resize'
break
default: break
}
		

html.style.cursor	= newCursorType // Avoid cursor's flickering
elem.style.cursor	= newCursorType
		

// Remove what is not necessary, and could have side effects!
elem.removeEventListener('mousemove', this._checkBorderHandler, false);
		

// Events on resizing state
/**
* We do not apply the mousemove event on the elem to resize it, but to the window to prevent the mousemove from slippe out of the elem to resize. This work bc we calculate things based on the mouse position
*/
window.addEventListener('mousemove', this._doResizeHandler, false);
window.addEventListener('mouseup', this._initResizerHandler, false);
}


_checkBorder(e) {
const elem = e.target
const borderSensitivity = 5
const coor = getCoordenatesCursor(e)
const onRightBorder		= ((coor.x + borderSensitivity) > elem.scrollWidth)
const onBottomBorder	= ((coor.y + borderSensitivity) > elem.scrollHeight)
const onBottomRightCorner = (onRightBorder && onBottomBorder)
		

if (onBottomRightCorner) {
elem.style.cursor = 'nwse-resize'
} else if (onRightBorder) {
elem.style.cursor = 'ew-resize'
} else if (onBottomBorder) {
elem.style.cursor = 'ns-resize'
} else {
elem.style.cursor = 'auto'
}
		

if (onRightBorder || onBottomBorder) {
elem.addEventListener('mousedown', this._onResizeHandler, false)
} else {
elem.removeEventListener('mousedown', this._onResizeHandler, false)
}
}
}


function getCoordenatesCursor(e) {
let elem = e.target;
	

// Get the Viewport-relative coordinates of cursor.
let viewportX = e.clientX
let viewportY = e.clientY
	

// Viewport-relative position of the target element.
let elemRectangle = elem.getBoundingClientRect()
	

// The  function returns the largest integer less than or equal to a given number.
let x = Math.floor(viewportX - elemRectangle.left) // - elem.scrollWidth
let y = Math.floor(viewportY - elemRectangle.top) // - elem.scrollHeight
	

return {x, y}
}


let resizerForCenter = new Resizer('center')
resizerForCenter.initResizer()


let resizerForLeft = new Resizer('left')
resizerForLeft.initResizer()


setTimeout(handler, 10000, true); // 10s


function handler() {
resizerForCenter.stopResizer()
}

body {
background-color: white;
}


#wrapper div {
/* box-sizing: border-box; */
position: relative;
float:left;
overflow: hidden;
height: 50px;
width: 50px;
padding: 3px;
}


#left {
background-color: blueviolet;
}
#center {
background-color:lawngreen ;
}
#right {
background: blueviolet;
}
#wrapper {
border: 5px solid hotpink;
display: inline-block;
	

}

<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>Resizer v0.0.1</title>
</head>
<body>
<div id="wrapper">
<div id="left">Left</div>
<div id="center">Center</div>
<div id="right">Right</div>
</div>
</body>
</html>

小开

just using the `mousemove` event in vanilla js

steps

add the mousemove to your target
listen to the target move event
get the pointer position, resize your target

codes

    const div = document.querySelector(`div.before`);
const box = document.querySelector(`div.container`);
box.addEventListener(`mousemove`, (e) => {
const {
offsetX,
offsetY,
} = e;
div.style.width = offsetX + `px`;
});

live demo

https://codepen.io/xgqfrms/full/wvMQqZL

refs

https://developer.mozilla.org/en-US/docs/Web/API/Element/mousemove_event

https://medium.com/the-z/making-a-resizable-div-in-js-is-not-easy-as-you-think-bda19a1bc53d

小开

// import
function get_difference(pre, mou) {
return {
x: mou.x - pre.x,
y: mou.y - pre.y
};
}


/*
if your panel is in a nested environment, which the parent container's width and height does not equa to document width
and height, for example, in an element `canvas`, then edit it to


function oMousePos(e) {
var rc = canvas.getBoundingClientRect();
return {
x: e.clientX - rc.left,
y: e.clientY - rc.top,
};
}
*/


function oMousePos(e) {
return {
x: e.clientX,
y: e.clientY,
};
}


function render_element(styles, el) {
for (const [kk, vv] of Object.entries(styles)) {
el.style[kk] = vv;
}
}


class MoveablePanel {


/*
prevent an element from moving out of window
*/
constructor(container, draggable, left, top) {
this.container = container;
this.draggable = draggable;
this.left = left;
this.top = top;
let rect = container.getBoundingClientRect();
this.width = rect.width;
this.height = rect.height;
this.status = false;


// initial position of the panel, should not be changed
this.original = {
left: left,
top: top
};


// current left and top postion
// {this.left, this.top}


// assign the panel to initial position
// initalize in registration
this.default();


if (!MoveablePanel._instance) {
MoveablePanel._instance = [];
}
MoveablePanel._instance.push(this);
}


mousedown(e) {
this.status = true;
this.previous = oMousePos(e)
}


mousemove(e) {
if (!this.status) {
return;
}
let pos = oMousePos(e);
let vleft = this.left + pos.x - this.previous.x;
let vtop = this.top + pos.y - this.previous.y;
let kleft, ktop;


if (vleft < 0) {
kleft = 0;
} else if (vleft > window.innerWidth - this.width) {
kleft = window.innerWidth - this.width;
} else {
kleft = vleft;
}


if (vtop < 0) {
ktop = 0;
} else if (vtop > window.innerHeight - this.height) {
ktop = window.innerHeight - this.height;
} else {
ktop = vtop;
}
this.container.style.left = `${kleft}px`;
this.container.style.top = `${ktop}px`;
}


/*
sometimes user move the cursor too fast which mouseleave is previous than mouseup
to prevent moving too fast and break the control, mouseleave is handled the same as mouseup
*/


mouseupleave(e) {
if (!this.status) {
return null;
}
this.status = false;
let pos = oMousePos(e);
let vleft = this.left + pos.x - this.previous.x;
let vtop = this.top + pos.y - this.previous.y;


if (vleft < 0) {
this.left = 0;
} else if (vleft > window.innerWidth - this.width) {
this.left = window.innerWidth - this.width;
} else {
this.left = vleft;
}


if (vtop < 0) {
this.top = 0;
} else if (vtop > window.innerHeight - this.height) {
this.top = window.innerHeight - this.height;
} else {
this.top = vtop;
}


this.show();
return true;
}


default () {
this.container.style.left = `${this.original.left}px`;
this.container.style.top = `${this.original.top}px`;
}


/*
panel with a higher z index will interupt drawing
therefore if panel is not displaying, set it with a lower z index that canvas


change index doesn't work, if panel is hiding, then we move it out
hide: record current position, move panel out
show: assign to recorded position


notice this position has nothing to do panel drag movement
they cannot share the same variable
*/


hide() {
// move to the right bottom conner
this.container.style.left = `${window.screen.width}px`;
this.container.style.top = `${window.screen.height}px`;
}


show() {
this.container.style.left = `${this.left}px`;
this.container.style.top = `${this.top}px`;
}
}
// end of import


class DotButton{
constructor(
width_px,
styles, // mainly pos, padding and margin, e.g. {top: 0, left: 0, margin: 0},
color,
color_hover,
border, // boolean
border_dismiss, // boolean: dismiss border when hover
){
this.width = width_px;
this.styles = styles;
this.color = color;
this.color_hover = color_hover;
this.border = border;
this.border_dismiss = border_dismiss;
}


create(_styles=null){
var el = document.createElement('div');
Object.keys(this.styles).forEach(kk=>{
el.style[kk] = `${this.styles[kk]}px`;
});
if(_styles){
Object.keys(_styles).forEach(kk=>{
el.style[kk] = `${this.styles[kk]}px`;
});
}
el.style.width = `${this.width}px`
el.style.height = `${this.width}px`
el.style.position = 'absolute';
el.style.left = `${this.left_px}px`;
el.style.top = `${this.top_px}px`;
el.style.background = this.color;
if(this.border){
el.style.border = '1px solid';
}
el.style.borderRadius = `${this.width}px`;


el.addEventListener('mouseenter', ()=>{
el.style.background = this.color_hover;
if(this.border_dismiss){
el.style.border = `1px solid ${this.color_hover}`;
}
});
el.addEventListener('mouseleave', ()=>{
el.style.background = this.color;
if(this.border_dismiss){
el.style.border = '1px solid';
}
});
return el;
}
}


function cursor_hover(el, default_cursor, to_cursor){
el.addEventListener('mouseenter', function(){
this.style.cursor = to_cursor;
}.bind(el));




el.addEventListener('mouseleave', function(){
this.style.cursor = default_cursor;
}.bind(el));
}


class FlexPanel extends MoveablePanel{
constructor(
parent_el,
top_px,
left_px,
width_px,
height_px,
background,
handle_width_px,
coner_vmin_ratio,
button_width_px,
button_margin_px,
){
super(
(()=>{
var el = document.createElement('div');
render_element(
{
position: 'fixed',
top: `${top_px}px`,
left: `${left_px}px`,
width: `${width_px}px`,
height: `${height_px}px`,
background: background,
},
el,
);
return el;
})(), // iife returns a container (panel el)
new DotButton(button_width_px, {top: 0, right: 0, margin: button_margin_px}, 'green', 'lightgreen', false, false).create(), // draggable
left_px, // left
top_px, // top
);


this.draggable.addEventListener('mousedown', e => {
e.preventDefault();
this.mousedown(e);
});


this.draggable.addEventListener('mousemove', e => {
e.preventDefault();
this.mousemove(e);
});


this.draggable.addEventListener('mouseup', e => {
e.preventDefault();
this.mouseupleave(e);
});


this.draggable.addEventListener('mouseleave', e => {
e.preventDefault();
this.mouseupleave(e);
});


this.parent_el = parent_el;
this.background = background;


// parent
this.width = width_px;
this.height = height_px;


this.handle_width_px = handle_width_px;
this.coner_vmin_ratio = coner_vmin_ratio;


this.panel_el = document.createElement('div');


// styles that won't change
this.panel_el.style.position = 'absolute';
this.panel_el.style.top = `${this.handle_width_px}px`;
this.panel_el.style.left = `${this.handle_width_px}px`;
this.panel_el.style.background = this.background;
    

this.handles = [
this.handle_top,
this.handle_left,
this.handle_bottom,
this.handle_right,


this.handle_lefttop,
this.handle_topleft,
this.handle_topright,
this.handle_righttop,
this.handle_rightbottom,
this.handle_bottomright,
this.handle_bottomleft,
this.handle_leftbottom,
] = Array.from({length: 12}, i => document.createElement('div'));


this.handles.forEach(el=>{
el.style.position = 'absolute';
});


this.handle_topleft.style.top = '0';
this.handle_topleft.style.left = `${this.handle_width_px}px`;


this.handle_righttop.style.right = '0';
this.handle_righttop.style.top = `${this.handle_width_px}px`;


this.handle_bottomright.style.bottom = '0';
this.handle_bottomright.style.right = `${this.handle_width_px}px`;


this.handle_leftbottom.style.left = '0';
this.handle_leftbottom.style.bottom = `${this.handle_width_px}px`;




this.handle_lefttop.style.left = '0';
this.handle_lefttop.style.top = '0';


this.handle_topright.style.top = '0';
this.handle_topright.style.right = '0';


this.handle_rightbottom.style.right = '0';
this.handle_rightbottom.style.bottom = '0';


this.handle_bottomleft.style.bottom = '0';
this.handle_bottomleft.style.left = '0';


this.update_ratio();


[
'ns-resize', // |
'ew-resize', // -
'ns-resize', // |
'ew-resize', // -


'nwse-resize', // \
'nwse-resize', // \
'nesw-resize', // /
'nesw-resize', // /
'nwse-resize', // \
'nwse-resize', // \
'nesw-resize', // /
'nesw-resize', // /
].map((dd, ii)=>{
cursor_hover(this.handles[ii], 'default', dd);
});


this.vtop = this.top;
this.vleft = this.left;
this.vwidth = this.width;
this.vheight = this.height;


this.update_ratio();


this.handles.forEach(el=>{
this.container.appendChild(el);
});


cursor_hover(this.draggable, 'default', 'move');


this.panel_el.appendChild(this.draggable);
this.container.appendChild(this.panel_el);
this.parent_el.appendChild(this.container);


[
this.edgemousedown,
this.verticalmousemove,
this.horizontalmousemove,
this.nwsemousemove,
this.neswmousemove,
this.edgemouseupleave,
] = [
this.edgemousedown.bind(this),
this.verticalmousemove.bind(this),
this.horizontalmousemove.bind(this),
this.nwsemousemove.bind(this),
this.neswmousemove.bind(this),
this.edgemouseupleave.bind(this),
];


this.handle_top.addEventListener('mousedown', e=>{this.edgemousedown(e, 'top')});
this.handle_left.addEventListener('mousedown', e=>{this.edgemousedown(e, 'left')});
this.handle_bottom.addEventListener('mousedown', e=>{this.edgemousedown(e, 'bottom')});
this.handle_right.addEventListener('mousedown', e=>{this.edgemousedown(e, 'right')});
this.handle_lefttop.addEventListener('mousedown', e=>{this.edgemousedown(e, 'lefttop')});
this.handle_topleft.addEventListener('mousedown', e=>{this.edgemousedown(e, 'topleft')});
this.handle_topright.addEventListener('mousedown', e=>{this.edgemousedown(e, 'topright')});
this.handle_righttop.addEventListener('mousedown', e=>{this.edgemousedown(e, 'righttop')});
this.handle_rightbottom.addEventListener('mousedown', e=>{this.edgemousedown(e, 'rightbottom')});
this.handle_bottomright.addEventListener('mousedown', e=>{this.edgemousedown(e, 'bottomright')});
this.handle_bottomleft.addEventListener('mousedown', e=>{this.edgemousedown(e, 'bottomleft')});
this.handle_leftbottom.addEventListener('mousedown', e=>{this.edgemousedown(e, 'leftbottom')});


this.handle_top.addEventListener('mousemove', this.verticalmousemove);
this.handle_left.addEventListener('mousemove', this.horizontalmousemove);
this.handle_bottom.addEventListener('mousemove', this.verticalmousemove);
this.handle_right.addEventListener('mousemove', this.horizontalmousemove);
this.handle_lefttop.addEventListener('mousemove', this.nwsemousemove);
this.handle_topleft.addEventListener('mousemove', this.nwsemousemove);
this.handle_topright.addEventListener('mousemove', this.neswmousemove);
this.handle_righttop.addEventListener('mousemove', this.neswmousemove);
this.handle_rightbottom.addEventListener('mousemove', this.nwsemousemove);
this.handle_bottomright.addEventListener('mousemove', this.nwsemousemove);
this.handle_bottomleft.addEventListener('mousemove', this.neswmousemove);
this.handle_leftbottom.addEventListener('mousemove', this.neswmousemove);


this.handle_top.addEventListener('mouseup', e=>{this.verticalmousemove(e); this.edgemouseupleave()});
this.handle_left.addEventListener('mouseup', e=>{this.horizontalmousemove(e); this.edgemouseupleave()});
this.handle_bottom.addEventListener('mouseup', e=>{this.verticalmousemove(e); this.edgemouseupleave()});
this.handle_right.addEventListener('mouseup', e=>{this.horizontalmousemove(e); this.edgemouseupleave()});
this.handle_lefttop.addEventListener('mouseup', e=>{this.nwsemousemove(e); this.edgemouseupleave()});
this.handle_topleft.addEventListener('mouseup', e=>{this.nwsemousemove(e); this.edgemouseupleave()});
this.handle_topright.addEventListener('mouseup', e=>{this.neswmousemove(e); this.edgemouseupleave()});
this.handle_righttop.addEventListener('mouseup', e=>{this.neswmousemove(e); this.edgemouseupleave()});
this.handle_rightbottom.addEventListener('mouseup', e=>{this.nwsemousemove(e); this.edgemouseupleave()});
this.handle_bottomright.addEventListener('mouseup', e=>{this.nwsemousemove(e); this.edgemouseupleave()});
this.handle_bottomleft.addEventListener('mouseup', e=>{this.neswmousemove(e); this.edgemouseupleave()});
this.handle_leftbottom.addEventListener('mouseup', e=>{this.neswmousemove(e); this.edgemouseupleave()});
    

this.handle_top.addEventListener('mouseleave', this.edgemouseupleave);
this.handle_left.addEventListener('mouseleave', this.edgemouseupleave);
this.handle_bottom.addEventListener('mouseleave', this.edgemouseupleave);
this.handle_right.addEventListener('mouseleave', this.edgemouseupleave);
this.handle_lefttop.addEventListener('mouseleave', this.edgemouseupleave);
this.handle_topleft.addEventListener('mouseleave', this.edgemouseupleave);
this.handle_topright.addEventListener('mouseleave', this.edgemouseupleave);
this.handle_righttop.addEventListener('mouseleave', this.edgemouseupleave);
this.handle_rightbottom.addEventListener('mouseleave', this.edgemouseupleave);
this.handle_bottomright.addEventListener('mouseleave', this.edgemouseupleave);
this.handle_bottomleft.addEventListener('mouseleave', this.edgemouseupleave);
this.handle_leftbottom.addEventListener('mouseleave', this.edgemouseupleave);
}


// box size change triggers corner handler size change
update_ratio(){
this.container.style.top = `${this.vtop}px`;
this.container.style.left = `${this.vleft}px`;
this.container.style.width = `${this.vwidth}px`;
this.container.style.height = `${this.vheight}px`;


this.panel_el.style.width = `${this.vwidth - 2 * this.handle_width_px}px`;
this.panel_el.style.height = `${this.vheight - 2 * this.handle_width_px}px`;


this.ratio = this.vwidth < this.vheight ? this.coner_vmin_ratio * this.vwidth : this.coner_vmin_ratio * this.vheight;
[
this.handle_top,
this.handle_bottom,
].forEach(el=>{
el.style.width = `${this.vwidth - 2 * this.ratio}px`;
el.style.height = `${this.handle_width_px}px`;
});


[
this.handle_left,
this.handle_right,
].forEach(el=>{
el.style.height = `${this.vheight - 2 * this.ratio}px`;
el.style.width = `${this.handle_width_px}px`;
});


this.handle_top.style.top = `0`;
this.handle_top.style.left = `${this.ratio}px`;


this.handle_left.style.top = `${this.ratio}px`;
this.handle_left.style.left = `0`;


this.handle_bottom.style.bottom = `0`;
this.handle_bottom.style.right = `${this.ratio}px`;


this.handle_right.style.bottom = `${this.ratio}px`;
this.handle_right.style.right = `0`;


[
this.handle_topright,
this.handle_bottomleft,
].forEach(el=>{
el.style.width = `${this.ratio}px`;
el.style.height = `${this.handle_width_px}px`;
});


[
this.handle_lefttop,
this.handle_rightbottom,
].forEach(el=>{
el.style.width = `${this.handle_width_px}px`;
el.style.height = `${this.ratio}px`;
});


[
this.handle_topleft,
this.handle_bottomright,
].forEach(el=>{
el.style.width = `${this.ratio - this.handle_width_px}px`;
el.style.height = `${this.handle_width_px}px`;
});


[
this.handle_righttop,
this.handle_leftbottom,
].forEach(el=>{
el.style.height = `${this.handle_width_px}px`;
el.style.width = `${this.ratio - this.handle_width_px}px`;
});
}


edgemousedown(e, flag){
this.previous = oMousePos(e);
this.flag = flag;
this.drag = true;
}


verticalmousemove(e){
if(this.drag){
// -
this.mouse = oMousePos(e);
var ydif = this.mouse.y - this.previous.y;
switch(this.flag){
case 'top':
this.vtop = this.top + ydif;
this.vheight = this.height - ydif;


this.vleft = this.left;
this.vwidth = this.width;
break;


case 'bottom':
this.vheight = this.height + ydif;


this.vtop = this.top;
this.vleft = this.left;
this.vwidth = this.width;
break;
}
this.update_ratio();
}
}


horizontalmousemove(e){
if(this.drag){
// |
this.mouse = oMousePos(e);
var xdif = this.mouse.x - this.previous.x;
switch(this.flag){
case 'left':
this.vleft = this.left + xdif;
this.vwidth = this.width - xdif;


this.vtop = this.top;
this.vheight = this.height;
break;


case 'right':
this.vwidth = this.width + xdif;
                

this.vtop = this.top;
this.vleft = this.left;
this.vheight = this.height;
break;
}
this.update_ratio();
}
}


nwsemousemove(e){
if(this.drag){
// \
this.mouse = oMousePos(e);
var ydif = this.mouse.y - this.previous.y;
var xdif = this.mouse.x - this.previous.x;
switch(this.flag){
case 'topleft':
this.vleft = this.left + xdif;
this.vtop = this.top + ydif;
this.vwidth = this.width - xdif;
this.vheight = this.height - ydif;
break;


case 'lefttop':
this.vleft = this.left + xdif;
this.vtop = this.top + ydif;
this.vwidth = this.width - xdif;
this.vheight = this.height - ydif;
break;


case 'bottomright':
this.vwidth = this.width + xdif;
this.vheight = this.height + ydif;


this.vtop = this.top;
this.vleft = this.left;
break;


case 'rightbottom':
this.vwidth = this.width + xdif;
this.vheight = this.height + ydif;


this.vtop = this.top;
this.vleft = this.left;
break;
}
this.update_ratio();
}
}


neswmousemove(e){
if(this.drag){
// /
this.mouse = oMousePos(e);
var ydif = this.mouse.y - this.previous.y;
var xdif = this.mouse.x - this.previous.x;
switch(this.flag){
case 'topright':
this.vtop = this.top + ydif;
this.vwidth = this.width + xdif;
this.vheight = this.height - ydif;


this.vleft = this.left;
break;


case 'righttop':
this.vtop = this.top + ydif;
this.vwidth = this.width + xdif;
this.vheight = this.height - ydif;


this.vleft = this.left;
break;


case 'bottomleft':
this.vleft = this.left + xdif;
this.vwidth = this.width - xdif;
this.vheight = this.height + ydif;


this.vtop = this.top;
break;


case 'leftbottom':
this.vleft = this.left + xdif;
this.vwidth = this.width - xdif;
this.vheight = this.height + ydif;


this.vtop = this.top;
break;
}
this.update_ratio();
}
}


edgemouseupleave(){
this.drag = false;
this.top = this.vtop;
this.left = this.vleft;
this.width = this.vwidth;
this.height = this.vheight;
}


mouseupleave(e){
if(super.mouseupleave(e)){
this.vtop = this.top;
this.vleft = this.left;
}
}
}




var fp = new FlexPanel(
document.body, // parent div container
20, // top margin
20, // left margin
200, // width
150, // height
'lightgrey', // background
20, // handle height when horizontal; handle width when vertical
0.2, // edge up and left resize bar width : top resize bar width = 1 : 5
35, // green move button width and height
2, // button margin
);


/*
this method creates an element for you
which you don't need to pass in a selected element


to manipuate dom element
fp.container -> entire panel
fp.panel_el -> inside panel
*/

Achieving functionalities fully requires a lot of hard coding. Please refer to the documentation, it will show you how to use each class as element.

小开

I'm not sure if this is what you are looking for, but you can always use CSS resize property and add it to an element using javascript; For example lets say you have a div element with the id myDiv and you want to make it resizable:

document.getElementById("myDiv").style.resize = "both";

here's the related links: Style resize Property CSS resize Property

小开

const onMouseDownEvent=(ev: React.DragEvent)=>{
let imgElem = (ev.target as HTMLImageElement);
let childElem = (ev.currentTarget && ev.currentTarget.childNodes && ev.currentTarget.childNodes[0]);
let original_height = parseFloat(getComputedStyle(imgElem, null).getPropertyValue('height').replace('px', ''));
let original_width = parseFloat(getComputedStyle(imgElem, null).getPropertyValue('width').replace('px', ''));
let original_Y =  imgElem.getBoundingClientRect().top;
let original_X =  imgElem.getBoundingClientRect().right;


ev.preventDefault();
var original_mouse_y = ev.pageY;
var original_mouse_x = ev.pageX;
document.addEventListener('mousemove', resize);
document.addEventListener('mouseup', stopResize);


function resize(mouseMoveEvent) {
const height = original_height + (mouseMoveEvent.pageY - original_mouse_y);
const width = original_width + (mouseMoveEvent.pageX - original_mouse_x);
        

imgElem.style.height = height + 'px';
mouseMoveEvent.target.childNodes[0].innerHTML = imgElem.style.height;


imgElem.style.width = width + 'px';
mouseMoveEvent.target.childNodes[0].innerHTML = imgElem.style.width;
}
    

function stopResize() {
document.removeEventListener('mousemove', resize)
}
}




<div onMouseDown={onMouseDownEvent} id="imgInCanvas" onDragStart={ onDragStartFromContainer } draggable="true"/>

小开

here is a example with resizer helpers in all sides and corners

element = document.getElementById("element")
makeResizable(element,10,10)
function makeResizable(element, minW = 100, minH = 100, size = 20)
{
const top = document.createElement('div');
top.style.width = '100%';
top.style.height = size + 'px';
top.style.backgroundColor = 'transparent';
top.style.position = 'absolute';
top.style.top = - (size/2) + 'px';
top.style.left = '0px';
top.style.cursor = 'n-resize';


top.addEventListener('mousedown',resizeYNegative())


element.appendChild(top);


const bottom = document.createElement('div');
bottom.style.width = '100%';
bottom.style.height = size + 'px';
bottom.style.backgroundColor = 'transparent';
bottom.style.position = 'absolute';
bottom.style.bottom = - (size/2) + 'px';
bottom.style.left = '0px';
bottom.style.cursor = 'n-resize';


bottom.addEventListener('mousedown',resizeYPositive())


element.appendChild(bottom);


const left = document.createElement('div');
left.style.width = size + 'px';
left.style.height = '100%';
left.style.backgroundColor = 'transparent';
left.style.position = 'absolute';
left.style.top = '0px';
left.style.left = - (size/2) + 'px';
left.style.cursor = 'e-resize';


left.addEventListener('mousedown',resizeXNegative())


element.appendChild(left);


const right = document.createElement('div');
right.style.width = size + 'px';
right.style.height = '100%';
right.style.backgroundColor = 'transparent';
right.style.position = 'absolute';
right.style.top = '0px';
right.style.right = - (size/2) + 'px';
right.style.cursor = 'e-resize';


right.addEventListener('mousedown',resizeXPositive())


element.appendChild(right);




const corner1 = document.createElement('div');
corner1.style.width = size + 'px';
corner1.style.height = size + 'px';
corner1.style.backgroundColor = 'transparent';
corner1.style.position = 'absolute';
corner1.style.top = - (size/2) + 'px';
corner1.style.left = - (size/2) + 'px';
corner1.style.cursor = 'nw-resize';


corner1.addEventListener('mousedown',resizeXNegative())
corner1.addEventListener('mousedown',resizeYNegative())
    

element.appendChild(corner1);


const corner2 = document.createElement('div');
corner2.style.width = size + 'px';
corner2.style.height = size + 'px';
corner2.style.backgroundColor = 'transparent';
corner2.style.position = 'absolute';
corner2.style.top = - (size/2) + 'px';
corner2.style.right = - (size/2) + 'px';
corner2.style.cursor = 'ne-resize';


corner2.addEventListener('mousedown',resizeXPositive())
corner2.addEventListener('mousedown',resizeYNegative())


element.appendChild(corner2);


const corner3 = document.createElement('div');
corner3.style.width = size + 'px';
corner3.style.height = size + 'px';
corner3.style.backgroundColor = 'transparent';
corner3.style.position = 'absolute';
corner3.style.bottom = - (size/2) + 'px';
corner3.style.left = - (size/2) + 'px';
corner3.style.cursor = 'sw-resize';


corner3.addEventListener('mousedown',resizeXNegative())
corner3.addEventListener('mousedown',resizeYPositive())


element.appendChild(corner3);


const corner4 = document.createElement('div');
corner4.style.width = size + 'px';
corner4.style.height = size + 'px';
corner4.style.backgroundColor = 'transparent';
corner4.style.position = 'absolute';
corner4.style.bottom = - (size/2) + 'px';
corner4.style.right = - (size/2) + 'px';
corner4.style.cursor = 'se-resize';


corner4.addEventListener('mousedown',resizeXPositive())
corner4.addEventListener('mousedown',resizeYPositive())


element.appendChild(corner4);
    

function get_int_style(key)
{
return parseInt(window.getComputedStyle(element).getPropertyValue(key));
}


function resizeXPositive()
{
let offsetX
function dragMouseDown(e) {
if(e.button !== 0) return
e = e || window.event;
e.preventDefault();
const {clientX} = e;
offsetX = clientX - element.offsetLeft - get_int_style('width');
document.addEventListener('mouseup', closeDragElement)
document.addEventListener('mousemove', elementDrag)
}
        

function elementDrag(e) {
const {clientX} = e;
let x = clientX - element.offsetLeft - offsetX
if(x < minW) x = minW;
element.style.width =  x + 'px';
}
        

function closeDragElement() {
document.removeEventListener("mouseup", closeDragElement);
document.removeEventListener("mousemove", elementDrag);
}
return dragMouseDown
}


function resizeYPositive()
{
let offsetY
function dragMouseDown(e) {
if(e.button !== 0) return
e = e || window.event;
e.preventDefault();
const {clientY} = e;
offsetY = clientY - element.offsetTop - get_int_style('height');
    

document.addEventListener('mouseup',closeDragElement)
document.addEventListener('mousemove',elementDrag)
}
        

function elementDrag(e) {
const {clientY} = e;
let y =  clientY - element.offsetTop - offsetY;
if(y < minH) y = minH;
element.style.height = y + 'px';
}
        

function closeDragElement() {
document.removeEventListener("mouseup", closeDragElement);
document.removeEventListener("mousemove", elementDrag);
}
return dragMouseDown
}


function resizeXNegative()
{
let offsetX
let startX
let startW
let maxX
function dragMouseDown(e) {
if(e.button !== 0) return
e = e || window.event;
e.preventDefault();
const {clientX} = e;
startX = get_int_style('left')
startW = get_int_style('width')
offsetX = clientX - startX;
maxX = startX + startW - minW
    

document.addEventListener('mouseup',closeDragElement)
document.addEventListener('mousemove',elementDrag)
}
        

function elementDrag(e) {
const {clientX} = e;
let x = clientX - offsetX
let w = startW + startX - x
if(w < minW) w = minW;
if(x > maxX) x = maxX;
element.style.left = x + 'px';
element.style.width = w + 'px';
}
        

function closeDragElement() {
document.removeEventListener("mouseup", closeDragElement);
document.removeEventListener("mousemove", elementDrag);
}
return dragMouseDown
}


function resizeYNegative()
{
let offsetY
let startY
let startH
let maxY
function dragMouseDown(e) {
if(e.button !== 0) return
e = e || window.event;
e.preventDefault();
const {clientY} = e;
startY = get_int_style('top')
startH = get_int_style('height')
offsetY = clientY - startY;
maxY = startY + startH - minH
    

document.addEventListener('mouseup',closeDragElement,false)
document.addEventListener('mousemove',elementDrag,false)
}
        

function elementDrag(e) {
const {clientY} = e;
let y =  clientY - offsetY
let h = startH + startY - y
if(h < minH) h = minH;
if(y > maxY) y = maxY;
element.style.top = y + 'px';
element.style.height = h + 'px';
}
        

function closeDragElement() {
document.removeEventListener("mouseup", closeDragElement);
document.removeEventListener("mousemove", elementDrag);
}
return dragMouseDown
}
}

 #element {
position: absolute;
background-color: #f1f1f1;
border: 1px solid #d3d3d3;
left: 40px;
top:  40px;
width: 100px;
height: 100px;
border-radius: 5px;
}

<div id="element"></div>

如何使 HTML 元素可调整大小使用纯 Javascript？

just using the mousemove event in vanilla js

steps

codes

live demo

refs

just using the `mousemove` event in vanilla js