Created
August 23, 2021 02:04
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Pure JavaScript docReady Function
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// add event cross browser | |
function addEvent(elem, event, fn) { | |
if (elem.addEventListener) { | |
elem.addEventListener(event, fn, false); | |
} else { | |
elem.attachEvent("on" + event, function () { | |
// set the this pointer same as addEventListener when fn is called | |
return fn.call(elem, window.event); | |
}); | |
} | |
} | |
(function (funcName, baseObj) { | |
// The public function name defaults to window.docReady | |
// but you can pass in your own object and own function name and those will be used | |
// if you want to put them in a different namespace | |
funcName = funcName || "docReady"; | |
baseObj = baseObj || window; | |
var readyList = []; | |
var readyFired = false; | |
var readyEventHandlersInstalled = false; | |
// call this when the document is ready | |
// this function protects itself against being called more than once | |
function ready() { | |
if (!readyFired) { | |
// this must be set to true before we start calling callbacks | |
readyFired = true; | |
for (var i = 0; i < readyList.length; i++) { | |
// if a callback here happens to add new ready handlers, | |
// the docReady() function will see that it already fired | |
// and will schedule the callback to run right after | |
// this event loop finishes so all handlers will still execute | |
// in order and no new ones will be added to the readyList | |
// while we are processing the list | |
readyList[i].fn.call(window, readyList[i].ctx); | |
} | |
// allow any closures held by these functions to free | |
readyList = []; | |
} | |
} | |
function readyStateChange() { | |
if (document.readyState === "complete") { | |
ready(); | |
} | |
} | |
// This is the one public interface | |
// docReady(fn, context); | |
// the context argument is optional - if present, it will be passed | |
// as an argument to the callback | |
baseObj[funcName] = function (callback, context) { | |
if (typeof callback !== "function") { | |
throw new TypeError("callback for docReady(fn) must be a function"); | |
} | |
// if ready has already fired, then just schedule the callback | |
// to fire asynchronously, but right away | |
if (readyFired) { | |
setTimeout(function () { | |
callback(context); | |
}, 1); | |
return; | |
} else { | |
// add the function and context to the list | |
readyList.push({ fn: callback, ctx: context }); | |
} | |
// if document already ready to go, schedule the ready function to run | |
if (document.readyState === "complete") { | |
setTimeout(ready, 1); | |
} else if (!readyEventHandlersInstalled) { | |
// otherwise if we don't have event handlers installed, install them | |
if (document.addEventListener) { | |
// first choice is DOMContentLoaded event | |
document.addEventListener("DOMContentLoaded", ready, false); | |
// backup is window load event | |
window.addEventListener("load", ready, false); | |
} else { | |
// must be IE | |
document.attachEvent("onreadystatechange", readyStateChange); | |
window.attachEvent("onload", ready); | |
} | |
readyEventHandlersInstalled = true; | |
} | |
}; | |
})("docReady", window); | |
// call it directly | |
docReady(function () { | |
document.getElementById("test1").innerHTML = "Hello Test 1"; | |
}); | |
// test calling docReady after window load and | |
// docReady has already fired | |
addEvent(window, "load", function () { | |
setTimeout(function () { | |
docReady(function () { | |
document.getElementById("test2").innerHTML = "Hello Test 2"; | |
}); | |
}, 1); | |
}); |
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