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<!DOCTYPE HTML> | |
<!-- zero-timeout.html, L. David Baron <[email protected]>, 2010-03-07, 2010-03-09 --> | |
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<html lang="en-US"> | |
<head> | |
<title>Demo: Using postMessage to do setTimeout with a real zero timeout</title> | |
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> | |
<script type="text/javascript"> | |
// BEGIN implementation of setZeroTimeout | |
// Only add setZeroTimeout to the window object, and hide everything | |
// else in a closure. | |
(function() { | |
var timeouts = []; | |
var messageName = "zero-timeout-message"; | |
// Like setTimeout, but only takes a function argument. There's | |
// no time argument (always zero) and no arguments (you have to | |
// use a closure). | |
function setZeroTimeout(fn) { | |
timeouts.push(fn); | |
window.postMessage(messageName, "*"); | |
} | |
function handleMessage(event) { | |
if (event.source == window && event.data == messageName) { | |
event.stopPropagation(); | |
if (timeouts.length > 0) { | |
var fn = timeouts.shift(); | |
fn(); | |
} | |
} | |
} | |
window.addEventListener("message", handleMessage, true); | |
// Add the one thing we want added to the window object. | |
window.setZeroTimeout = setZeroTimeout; | |
})(); | |
// END implementation of setZeroTimeout | |
// BEGIN demo that uses setZeroTimeout | |
function runtest() { | |
var output = document.getElementById("output"); | |
var outputText = document.createTextNode(""); | |
output.appendChild(outputText); | |
function printOutput(line) { | |
outputText.data += line + "\n"; | |
} | |
var i = 0; | |
var startTime = Date.now(); | |
function test1() { | |
if (++i == 100) { | |
var endTime = Date.now(); | |
printOutput("100 iterations of setZeroTimeout took " + | |
(endTime - startTime) + " milliseconds."); | |
i = 0; | |
startTime = Date.now(); | |
setTimeout(test2, 0); | |
} else { | |
setZeroTimeout(test1); | |
} | |
} | |
setZeroTimeout(test1); | |
function test2() { | |
if (++i == 100) { | |
var endTime = Date.now(); | |
printOutput("100 iterations of setTimeout(0) took " + | |
(endTime - startTime) + " milliseconds."); | |
} else { | |
setTimeout(test2, 0); | |
} | |
} | |
} | |
// END demo that uses setZeroTimeout | |
</script> | |
</head> | |
<body onload="runtest()"> | |
<h1>Demo: Using postMessage to do setTimeout with a real zero timeout</h1> | |
<pre id="output"></pre> | |
</body> | |
</html> |
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