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@ajtatum
Created Aug 23, 2021
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Pure JavaScript docReady Function
// 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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