静态定位和相对定位的区别

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Position relative lets you use top/bottom/left/right for positioning. Static won't let you do this unless you use margin parameters. There's a difference between Top and margin-top.

You won't need to use static much as it's default

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最佳答案

Static positioning is the default positioning model for elements. They are displayed in the page where they rendered as part of normal HTML flow. Statically positioned elements don't obey left, top, right and bottom rules:

statically-positioned elements obey normal HTML flow.

Relative positioning allows you to specify a specific offset (left, top etc) which is relative to the element's normal position in HTML flow. So if I have a textbox inside a div I could apply relative positioning on the textbox to have it display at specific place relative to where it would normally be placed within the div:

relatively-positioned elements obey HTML flow, but provide the ability to adjust their position relative to their normal position in HTML flow.

There is also absolute positioning - whereby you specify the exact location of the element relative to the entire document, or the next relatively positioned element further up the element tree:

absolutely-positioned elements are taken out of HTML flow and can be positioned at a specific place in the document...

And when a position: relative is applied to a parent element in the hierarchy:

...or positioned relative to the first parent element in the HTML tree that is relatively positioned.

Note how our absolutely-position element is bound by the relatively-positioned element.

And lastly there is fixed. Fixed positioning restricts an element to a specific position in the viewport, which stays in place during scroll:

fixed-positioned elements are also taken out of HTML flow, but are not bound by the viewport and will not scroll with the page.

You may also observe the behaviour that fixed-positioned elements do not cause scroll because they are not considered to be bound by the viewport:

fixed-positioned elements have no effect on scroll.

Whereas absolutely-positioned elements are still bound by the viewport and will cause scrolling:

absolutely-positioned elements are still affected by the boundaries of the viewport, unless overflow is used on a parent element.

..unless of course your parent element uses overflow: ? to determine the behaviour of the scroll (if any).

With absolute positioning and fixed positioning, the elements are taken out of HTML flow.

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You can see a simple overview here: W3School

Also, if I recall correctly, when declaring an element relative, it will by default stay in the same place as it otherwise should, but you gain the ability to absolutely position elements inside it relatively to this element, which I've found very useful in the past.

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Relative position is relative to the normal flow. The relative position of that element (with offsets) is relative to the position where that element would have been normally if not moved.

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Matthew Abbott has a really good answer.

Absolute and relative positioned items obey top, left, right and bottom commands (offsets) where static positioned items do not.

Relatively positioned items move offsets from where they would normally be in the html.

Absolute positioned items move offsets from the document or the next relatively positioned element up the DOM tree.

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In answer to "why CSS would still implement position: static;" in one scenerio, using position:relative for a parent and position:absolute for the child limits the scaling width of the child. In a horizontal menu system, where you could have 'columns' of links, using 'width:auto' does not work with relative parents. In this case, changing it to 'static' will allow the width to be variable dependent on the content within.

I spent a good few hours wondering why I couldn't get my container to adjust based on the amount of content within it. Hope this helps!

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Static: By default the position of elements is static. If you add property such as top, bottom, right, or left nothing will be implemented.

div{
width:200px;
height:200px;
background-color:yellow;
display:inline-block;
}


#middle{
background-color:pink;
}


#static #middle{
position:static;
top:100px;
}

<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<link rel="stylesheet" href="style.css">
<title>Document</title>
</head>
<body>
<h1>Position Property</h1>
<section id="static">
<h2>Static</h2>
<div></div>
<div id="middle"></div>
<div></div>
</section>
</body>
</html>

Relative: The change in position will be relevant to that div's original place.

div{
width:200px;
height:200px;
background-color:yellow;
display:inline-block;
}


#middle{
background-color:pink;
}


#relative #middle{
position:relative;
top:100px;
left:100px;
}

<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<link rel="stylesheet" href="style.css">
<title>Document</title>
</head>
<body>
<h1>Position Property</h1>
<section id="relative">
<h2>Relative</h2>
<div></div>
<div id="middle"></div>
<div></div>
</section>


</body>
</html>

Absolute: It is positioned relative to its closest positioned ancestor, if any; otherwise, it is placed relative to the initial containing block. Source:MDN

div{
width:200px;
height:200px;
background-color:yellow;
display:inline-block;
}


#middle{
background-color:pink;
}


#absolute{
position:relative;
}


#absolute #middle{
position:absolute;
top:10px;
left:10px;
}

<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<link rel="stylesheet" href="style.css">
<title>Document</title>
</head>
<body>
<h1>Position Property</h1>
<section id="absolute">
<h2>Absolute</h2>
<div></div>
<div id="middle"></div>
<div></div>
</section>


</body>
</html>

Fixed: The fixed property would stay at the same place even after we scroll the page. The position is relative to the containing block always.

div{
width:200px;
height:200px;
background-color:yellow;
display:inline-block;
}


#middle{
background-color:pink;
}


#fixed #middle{
position:fixed;
top:10px;
left:10px;
}

<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<link rel="stylesheet" href="style.css">
<title>Document</title>
</head>
<body>
<h1>Position Property</h1>
<section id="fixed">
<h2>Fixed</h2>
<div></div>
<div id="middle"></div>
<div></div>
</section>
</body>
</html>