使用 HTML5和 iPad 捕获签名

//init
let r = document.getElementById('r'),
p = document.getElementById('p'),
signaturePath = '',
isDown = false,
svg = document.getElementById('sig_panel'),
b_show = document.getElementById('show'),
b_clear = document.getElementById('clear'),
pathdata = document.getElementById('pathdata');


//drawing functions
function isTouchEvent(e) {
return e.type.match(/^touch/);
}


function getCoords(e) {
if (isTouchEvent(e)) {
return e.targetTouches[0].clientX + ',' + e.targetTouches[0].clientY;
}
return e.clientX + ',' + e.clientY;
}


function down(e) {
signaturePath += 'M' + getCoords(e) + ' ';
p.setAttribute('d', signaturePath);
isDown = true;


if (isTouchEvent(e)) e.preventDefault();
}


function move(e) {
if (isDown) {
signaturePath += 'L' + getCoords(e) + ' ';
p.setAttribute('d', signaturePath);
}


if (isTouchEvent(e)) e.preventDefault();
}


function up(e) {
isDown = false;


if (isTouchEvent(e)) e.preventDefault();
}


//input handlers
r.addEventListener('touchstart', down, false);
r.addEventListener('touchmove', move, false);
r.addEventListener('touchend', up, false);
r.addEventListener('mousedown', down, false);
r.addEventListener('mousemove', move, false);
r.addEventListener('mouseup', up, false);
r.addEventListener('mouseout', up, false);


//helper functions
function clearSignature() {
pathdata.textContent = '';
signaturePath = '';
p.setAttribute('d', '');
}


function getSignature() {
pathdata.textContent = signaturePath;
return signaturePath;
}


//button handlers
b_show.addEventListener('click', getSignature);
b_clear.addEventListener('click', clearSignature);

svg {
margin: .5em;
border: 1px solid gray;
border-radius: .5em;
}


.flex {
display: flex;
}


button {
margin: .5em;
}


#pathdata {
font-family: monospace;
background: #ddd;
padding: 1em;
margin: 1em .5em;
}

<svg id="sig_panel" xmlns="http://www.w3.org/2000/svg" width="300" height="100" viewBox="0 0 300 100">
<rect id="r" width="300" height="100" fill="#ffa"/>
<line x1="0" y1="80" x2="300" y2="80" stroke="#666" stroke-width="1" stroke-dasharray="3" shape-rendering="crispEdges" pointer-events="none"/>
<path id="p" stroke="navy" stroke-width="2" fill="none" pointer-events="none"/>
</svg>
<div class="flex">
<button id="show">Show signaure path data</button>
<button id="clear">Clear signature</button>
</div>
<div id="pathdata"></div>