Related
<script src="/blog/js/jquery.min.js"></script>
<script src="/blog/js/templatemo-script.js"></script>
<script src="/blog/js/jquery_ui.js"></script>
<script>
function change_page(num) {
<-- This function takes the num, and adds that to the page number in session storage, and -->
<-- updates the page -->
}
function startup() {
sessionStorage.setItem('page','1');
document.getElementById('prev').addEventListener('click',prev);
document.getElementById('next').addEventListener('click',next);
change_page('0');
}
function prev() {
change_page('-1');
}
function next() {
change_page('1');
}
document.addEventListener('load',startup);
</script>
I'm currently trying to build a blog template. On my page, there are post slots that my function change_page loads blog posts onto depending on the current page in sessionStorage (num is added to the page in sessionStorage). There are also buttons with ids prev, next that do the obvious.
Currently, this code doesn't work, since the function startup() is not being called. To see the full code, see this. To see the output, see this.
What am I doing wrong here? (And no, it has nothing to do with the fact that the numbers are strings).
The load event fires on the window, not the document.
You're listening for it too low down.
Aside: there doesn't seem to be any need to wait for all the document's dependencies to load here. You should probably use the DOMContentLoaded event instead.
function change_page(num) {}
function startup() {
console.log("The start up function runs");
sessionStorage.setItem('page', '1');
document.getElementById('prev').addEventListener('click', prev);
document.getElementById('next').addEventListener('click', next);
change_page('0');
}
function prev() {
change_page('-1');
}
function next() {
change_page('1');
}
window.addEventListener('load', startup);
Just wondering if the amount of document.ready calls affects page load speed.
Is there a way in Gulp / Grunt to uglify / minify JS by removing seperate document ready functions?
Just check it!
I don't see significant difference in Chrome.
As I know, it was critical for IE8, but didn't check this fact.
IE11 shows 2 seconds on the first snippet, when the others take 200 ms only.
Also, seems like jQuery already aggregates load events.
Don't forget
When you are running same code in one tab, browser remembers something and runs it faster.
Reload the page is not enought. Open a new tab instead.
After opening a new tab, run snippets in different order.
If the snippet is ran first on the tab, it will get additional slowdown, comparing the other three.
for (var q=0; q<1000; ++q) {
document.addEventListener('DOMContentLoaded', (function (i) {
console.log(i);
}).bind(null, q));
}
document.addEventListener('DOMContentLoaded', function () {
document.querySelector('output').textContent = performance.now().toFixed(3);
});
<output></output>
document.addEventListener('DOMContentLoaded', function () {
for (var q=0; q<1000; ++q) {
(function (i) {
console.log(i)
}).bind(null, q)();
document.querySelector('output').textContent = performance.now().toFixed(3);
}
});
<output></output>
for (var q=0; q<1000; ++q) {
$((function (i) {
console.log(i);
}).bind(null, q));
}
$(function () {
document.querySelector('output').textContent = performance.now().toFixed(3);
});
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<output></output>
$(function () {
for (var q=0; q<1000; ++q) {
(function (i) {
console.log(i)
}).bind(null, q)();
document.querySelector('output').textContent = performance.now().toFixed(3);
}
});
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<output></output>
Maybe it's just me as a JavaScript avoider, but none of the scripts have document.ready inside. If you JS guys talk about document.ready, that's a synonym for addEventListener('DOMContentLoaded')?
There are two events: DOMContentLoaded and load (window.onload). First of them occures when the body pasring is complete, but some assets are loading still. The second - when the page is completely loaded. First one is nice for running scripts with dom manipulations, but browsers not always had support of it.
So jQuery uses the first of these two events and classic form of subscription was
$(document).ready(function () {
// ...
});
but after some versions if was simplified to passing function directly into jQuery:
$(function () {
// ...
});
So in vanilla examples I'm using the first of 2 events, and in jQuery examples I'm using the short form of subscription on it. As browsers without support of this event are very old it's correct to assume that jQuery always uses DOMContentLoaded (probably the load way is removed in version 2 - didn't check it, but see no reasons to keep it there).
Many document ready calls shouldn't affect much the application performance. The best solution may be having only one and init there all you need. But it depends on your application structure and you should be more confortable having more than one. Anyway, I don't think there is any Gulp task that wraps different ready functions in one, because it will touch the application logic.
You can have multiple ones, but it's not always the neatest thing to do. Try not to overuse them, as it will seriously affect readability. Other than that , it's perfectly legal.
It's also worth noting that a function defined within one $(document).ready block cannot be called from another $(document).ready block.
$(document).ready(function() {
alert('hello1');
function saySomething() {
alert('something');
}
saySomething();
});
$(document).ready(function() {
alert('hello2');
saySomething();
});
output was
hello1
something
hello2
Check this post and this one
Yes, you can use multiple document ready handler, there is no special advantage even though you can use jQuery code in several place. You can’t use the variable inside one in another since those are in different scope.
Actually jQuery event handler pushing function for execution in
queue of a particular event. When event is fired all functions
executes one by one from particular events row/stack/queue based on
return value of parent sequential function.
BUT
There is one thing to note that each $(document).ready() function call
must return. If an exception is thrown in one, subsequent calls will
never be run.
$(document).ready(function() {
document.write('<h3>In First ready function</h3>');
var foo = function() {
console.log('inside foo');
}
document.write("foo:" +(typeof foo)+"<br>");
document.write("bar:" +(typeof bar)+"<br>");
});
$(document).ready(function() {
document.write('<h3>In Second ready function</h3>');
var bar=function bar() {
console.log('inside bar');
}
document.write("foo:" +(typeof foo)+"<br>");
document.write("bar:" +(typeof bar)+"<br>");
});
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
Actually jQuery $(document).ready() method is attach function with DOMContentLoaded event using addEventListener method.
Yes you can have multiple instance of it on a single page. There is no particular advantage. All will get executed on first called first run basis.
I am wondering if there is a way to execute a JavaScript function once only on the first ever page load and then not execute on any subsequent reloads.
Is there a way I can go about doing this?
The code below will execute once the onload event fires. The statement checks if the onetime function has NOT been executed before by making use of a flag (hasCodeRunBefore), which is then stored in localStorage.
window.onload = function () {
if (localStorage.getItem("hasCodeRunBefore") === null) {
/** Your code here. **/
localStorage.setItem("hasCodeRunBefore", true);
}
}
Note: If the user clears their browsers' localStorage by any means, then the function will run again because the flag (hasCodeRunBefore) will have been removed.
Good news...
Using localStorage can be tedious because of operators and long winded function names. I created a basic module to simplify this, so the above code would be replaced with:
window.onload = function () {
if (!ls.exists('has_code_run_before')) {
/** Your code here... **/
ls.set.single('has_code_run_before', true);
/** or... you can use a callback. **/
ls.set.single('has_code_run_before', true, function () {
/** Your code here... **/
});
}
};
Update #1
Per #PatrickRoberts comment, you can use the in operator to see if a variable key exists in localStorage, so
if (localStorage.getItem('hasCodeRunBefore') === null)
becomes
if (!('hasCodeRunBefore' in localStorage))
and is less verbose and a lot cleaner.
Secondly, you can set values as you would an object (localStorage.hasCodeRunBefore = true) though it will be stored as a string, not as boolean (or whatever data type your value is).
function toBeExecutedOnFirstLoad(){
// ...
}
if(localStorage.getItem('first') === null){
toBeExecutedOnFirstLoad();
localStorage.setItem('first','nope!');
}
All JavaScript must execute every time a page loads. If the script is on the page, it will execute.
The logic that is executed within the JavaScript included on the page may execute in a different manner depending on the page state, input provided, and any other signals it receives, be it from the server or the client.
If you're using a server side language, you might choose to render a script conditionally, such as the first time a user logs in.
If you need to include the javascript irrespective of context, then you need to listen to other signals.
The simple modern solution is to make use of localStorage. localStorage can be used to store custom string values on custom key values for any given domain.
The code to make use of this would look like:
if (localStorage['...my key here...'] === '...my expected value here...') {
// The page has been visited before
} else {
// The page has not been visited before
// OR
// The user or script has cleared the localStorage value
}
localStorage['...my key here...'] = '...my expected value here...';
That's all well and good if you just need things to work on the client alone. Sometimes you might need the server to know whether or not the page has been visited before.
The (less)simple solution is to use document.cookie:
if (/(?:^|;\s*)...my key here...=...my expected value here...(?:;|$)/.test(document.cookie)) {
// the page has been visited before
} else {
// The page has not been visited before
// OR
// The user or script has cleared the cookie
}
document.cookie = '...my key here...=...my expected value here...';
If you need to defer the execution until the page has finished loading, then simply include the script in an onload callback, either by assigning the event to the window:
window.onload = function () {
// do stuff when the page has loaded
//this will override any other scripts that may have been assigned to .onload
};
or by binding the event handler to the window:
window.addEventListener('load', function () {
// do stuff when the page has loaded
}, false);
It depends on what first page load means to you. It's subjective.
If you want the function to fire once the DOM has been parsed, but only the HTML and no other external resources, bind it to the DOMContentLoaded event.
document.addEventListener('DOMContentLoaded', fn);
Otherwise, if you want to wait for external resources to be loaded and then fire the event, you should bind it to the window object's load event like so:
window.addEventListener('load', fn);
Here are some links from the Mozilla Developer Network that explain the what I just said in more detail:
https://developer.mozilla.org/en-US/docs/Web/Events/load
https://developer.mozilla.org/en-US/docs/Web/Events/DOMContentLoaded
Good luck!
I was facing something similar, the difference in my case was, I wanted to run a code whenever a new instance was being created I needed a certain code to execute, and then later for the rest of the reloads that code should not execute.
For that similar to localStorage solutions above use session storage instead:
fun_RunOnlyOnFirstPageLoad(){}
if(!$window.sessionStorage.getItem(hasRunBefore)){
fun_RunOnlyOnFirstPageLoad();
$window.sessionStorage.setItem(hasRunBefore, true);
}
using the window.sessionStorage instead stores the value only for that session.
this way once the tab is closed (session is over, that value is wiped out) and on every new instantiation, the code is executed.
This question already has answers here:
How to make JavaScript execute after page load?
(25 answers)
Closed 1 year ago.
I am using following code to execute some statements after page load.
<script type="text/javascript">
window.onload = function () {
newInvite();
document.ag.src="b.jpg";
}
</script>
But this code does not work properly. The function is called even if some images or elements are loading. What I want is to call the function the the page is loaded completely.
this may work for you :
document.addEventListener('DOMContentLoaded', function() {
// your code here
}, false);
or
if your comfort with jquery,
$(document).ready(function(){
// your code
});
$(document).ready() fires on DOMContentLoaded, but this event is not being fired consistently among browsers. This is why jQuery will most probably implement some heavy workarounds to support all the browsers. And this will make it very difficult to "exactly" simulate the behavior using plain Javascript (but not impossible of course).
as Jeffrey Sweeney and J Torres suggested, i think its better to have a setTimeout function, before firing the function like below :
setTimeout(function(){
//your code here
}, 3000);
JavaScript
document.addEventListener('readystatechange', event => {
// When HTML/DOM elements are ready:
if (event.target.readyState === "interactive") { //does same as: ..addEventListener("DOMContentLoaded"..
alert("hi 1");
}
// When window loaded ( external resources are loaded too- `css`,`src`, etc...)
if (event.target.readyState === "complete") {
alert("hi 2");
}
});
same for jQuery:
$(document).ready(function() { //same as: $(function() {
alert("hi 1");
});
$(window).load(function() {
alert("hi 2");
});
NOTE: - Don't use the below markup ( because it overwrites other same-kind declarations ) :
document.onreadystatechange = ...
I'm little bit confuse that what you means by page load completed, "DOM Load" or "Content Load" as well? In a html page load can fire event after two type event.
DOM load: Which ensure the entire DOM tree loaded start to end. But not ensure load the reference content. Suppose you added images by the img tags, so this event ensure that all the img loaded but no the images properly loaded or not. To get this event you should write following way:
document.addEventListener('DOMContentLoaded', function() {
// your code here
}, false);
Or using jQuery:
$(document).ready(function(){
// your code
});
After DOM and Content Load: Which indicate the the DOM and Content load as well. It will ensure not only img tag it will ensure also all images or other relative content loaded. To get this event you should write following way:
window.addEventListener('load', function() {...})
Or using jQuery:
$(window).on('load', function() {
console.log('All assets are loaded')
})
If you can use jQuery, look at load. You could then set your function to run after your element finishes loading.
For example, consider a page with a simple image:
<img src="book.png" alt="Book" id="book" />
The event handler can be bound to the image:
$('#book').load(function() {
// Handler for .load() called.
});
If you need all elements on the current window to load, you can use
$(window).load(function () {
// run code
});
If you cannot use jQuery, the plain Javascript code is essentially the same amount of (if not less) code:
window.onload = function() {
// run code
};
If you wanna call a js function in your html page use onload event. The onload event occurs when the user agent finishes loading a window or all frames within a FRAMESET. This attribute may be used with BODY and FRAMESET elements.
<body onload="callFunction();">
....
</body>
You're best bet as far as I know is to use
window.addEventListener('load', function() {
console.log('All assets loaded')
});
The #1 answer of using the DOMContentLoaded event is a step backwards since the DOM will load before all assets load.
Other answers recommend setTimeout which I would strongly oppose since it is completely subjective to the client's device performance and network connection speed. If someone is on a slow network and/or has a slow cpu, a page could take several to dozens of seconds to load, thus you could not predict how much time setTimeout will need.
As for readystatechange, it fires whenever readyState changes which according to MDN will still be before the load event.
Complete
The state indicates that the load event is about to fire.
This way you can handle the both cases - if the page is already loaded or not:
document.onreadystatechange = function(){
if (document.readyState === "complete") {
myFunction();
}
else {
window.onload = function () {
myFunction();
};
};
}
you can try like this without using jquery
window.addEventListener("load", afterLoaded,false);
function afterLoaded(){
alert("after load")
}
Alternatively you can try below.
$(window).bind("load", function() {
// code here });
This works in all the case. This will trigger only when the entire page is loaded.
window.onload = () => {
// run in onload
setTimeout(() => {
// onload finished.
// and execute some code here like stat performance.
}, 10)
}
If you're already using jQuery, you could try this:
$(window).bind("load", function() {
// code here
});
I can tell you that the best answer I found is to put a "driver" script just after the </body> command. It is the easiest and, probably, more universal than some of the solutions, above.
The plan: On my page is a table. I write the page with the table out to the browser, then sort it with JS. The user can resort it by clicking column headers.
After the table is ended a </tbody> command, and the body is ended, I use the following line to invoke the sorting JS to sort the table by column 3. I got the sorting script off of the web so it is not reproduced here. For at least the next year, you can see this in operation, including the JS, at static29.ILikeTheInternet.com. Click "here" at the bottom of the page. That will bring up another page with the table and scripts. You can see it put up the data then quickly sort it. I need to speed it up a little but the basics are there now.
</tbody></body><script type='text/javascript'>sortNum(3);</script></html>
MakerMikey
I tend to use the following pattern to check for the document to complete loading. The function returns a Promise (if you need to support IE, include the polyfill) that resolves once the document completes loading. It uses setInterval underneath because a similar implementation with setTimeout could result in a very deep stack.
function getDocReadyPromise()
{
function promiseDocReady(resolve)
{
function checkDocReady()
{
if (document.readyState === "complete")
{
clearInterval(intervalDocReady);
resolve();
}
}
var intervalDocReady = setInterval(checkDocReady, 10);
}
return new Promise(promiseDocReady);
}
Of course, if you don't have to support IE:
const getDocReadyPromise = () =>
{
const promiseDocReady = (resolve) =>
{
const checkDocReady = () =>
((document.readyState === "complete") && (clearInterval(intervalDocReady) || resolve()));
let intervalDocReady = setInterval(checkDocReady, 10);
}
return new Promise(promiseDocReady);
}
With that function, you can do the following:
getDocReadyPromise().then(whatIveBeenWaitingToDo);
call a function after complete page load set time out
setTimeout(function() {
var val = $('.GridStyle tr:nth-child(2) td:nth-child(4)').text();
for(var i, j = 0; i = ddl2.options[j]; j++) {
if(i.text == val) {
ddl2.selectedIndex = i.index;
break;
}
}
}, 1000);
Try this jQuery:
$(function() {
// Handler for .ready() called.
});
Put your script after the completion of body tag...it works...
This question already has answers here:
$(document).ready equivalent without jQuery
(39 answers)
Closed 6 years ago.
With jQuery, we all know the wonderful .ready() function:
$('document').ready(function(){});
However, let's say I want to run a function that is written in standard JavaScript with no library backing it, and that I want to launch a function as soon as the page is ready to handle it. What's the proper way to approach this?
I know I can do:
window.onload="myFunction()";
Or I can use the body tag:
<body onload="myFunction()">
Or I can even try at the bottom of the page after everything, but the end body or html tag like:
<script type="text/javascript">
myFunction();
</script>
What is a cross-browser(old/new)-compliant method of issuing one or more functions in a manner like jQuery's $.ready()?
The simplest thing to do in the absence of a framework that does all the cross-browser compatibility for you is to just put a call to your code at the end of the body. This is faster to execute than an onload handler because this waits only for the DOM to be ready, not for all images to load. And, this works in every browser.
<!doctype html>
<html>
<head>
</head>
<body>
Your HTML here
<script>
// self executing function here
(function() {
// your page initialization code here
// the DOM will be available here
})();
</script>
</body>
</html>
For modern browsers (anything from IE9 and newer and any version of Chrome, Firefox or Safari), if you want to be able to implement a jQuery like $(document).ready() method that you can call from anywhere (without worrying about where the calling script is positioned), you can just use something like this:
function docReady(fn) {
// see if DOM is already available
if (document.readyState === "complete" || document.readyState === "interactive") {
// call on next available tick
setTimeout(fn, 1);
} else {
document.addEventListener("DOMContentLoaded", fn);
}
}
Usage:
docReady(function() {
// DOM is loaded and ready for manipulation here
});
If you need full cross browser compatibility (including old versions of IE) and you don't want to wait for window.onload, then you probably should go look at how a framework like jQuery implements its $(document).ready() method. It's fairly involved depending upon the capabilities of the browser.
To give you a little idea what jQuery does (which will work wherever the script tag is placed).
If supported, it tries the standard:
document.addEventListener('DOMContentLoaded', fn, false);
with a fallback to:
window.addEventListener('load', fn, false )
or for older versions of IE, it uses:
document.attachEvent("onreadystatechange", fn);
with a fallback to:
window.attachEvent("onload", fn);
And, there are some work-arounds in the IE code path that I don't quite follow, but it looks like it has something to do with frames.
Here is a full substitute for jQuery's .ready() written in plain javascript:
(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);
The latest version of the code is shared publicly on GitHub at https://github.com/jfriend00/docReady
Usage:
// pass a function reference
docReady(fn);
// use an anonymous function
docReady(function() {
// code here
});
// pass a function reference and a context
// the context will be passed to the function as the first argument
docReady(fn, context);
// use an anonymous function with a context
docReady(function(context) {
// code here that can use the context argument that was passed to docReady
}, ctx);
This has been tested in:
IE6 and up
Firefox 3.6 and up
Chrome 14 and up
Safari 5.1 and up
Opera 11.6 and up
Multiple iOS devices
Multiple Android devices
Working implementation and test bed: http://jsfiddle.net/jfriend00/YfD3C/
Here's a summary of how it works:
Create an IIFE (immediately invoked function expression) so we can have non-public state variables.
Declare a public function docReady(fn, context)
When docReady(fn, context) is called, check if the ready handler has already fired. If so, just schedule the newly added callback to fire right after this thread of JS finishes with setTimeout(fn, 1).
If the ready handler has not already fired, then add this new callback to the list of callbacks to be called later.
Check if the document is already ready. If so, execute all ready handlers.
If we haven't installed event listeners yet to know when the document becomes ready, then install them now.
If document.addEventListener exists, then install event handlers using .addEventListener() for both "DOMContentLoaded" and "load" events. The "load" is a backup event for safety and should not be needed.
If document.addEventListener doesn't exist, then install event handlers using .attachEvent() for "onreadystatechange" and "onload" events.
In the onreadystatechange event, check to see if the document.readyState === "complete" and if so, call a function to fire all the ready handlers.
In all the other event handlers, call a function to fire all the ready handlers.
In the function to call all the ready handlers, check a state variable to see if we've already fired. If we have, do nothing. If we haven't yet been called, then loop through the array of ready functions and call each one in the order they were added. Set a flag to indicate these have all been called so they are never executed more than once.
Clear the function array so any closures they might be using can be freed.
Handlers registered with docReady() are guaranteed to be fired in the order they were registered.
If you call docReady(fn) after the document is already ready, the callback will be scheduled to execute as soon as the current thread of execution completes using setTimeout(fn, 1). This allows the calling code to always assume they are async callbacks that will be called later, even if later is as soon as the current thread of JS finishes and it preserves calling order.
If you are doing VANILLA plain JavaScript without jQuery, then you must use (Internet Explorer 9 or later):
document.addEventListener("DOMContentLoaded", function(event) {
// Your code to run since DOM is loaded and ready
});
Above is the equivalent of jQuery .ready:
$(document).ready(function() {
console.log("Ready!");
});
Which ALSO could be written SHORTHAND like this, which jQuery will run after the ready even occurs.
$(function() {
console.log("ready!");
});
NOT TO BE CONFUSED with BELOW (which is not meant to be DOM ready):
DO NOT use an IIFE like this that is self executing:
Example:
(function() {
// Your page initialization code here - WRONG
// The DOM will be available here - WRONG
})();
This IIFE will NOT wait for your DOM to load. (I'm even talking about latest version of Chrome browser!)
I would like to mention some of the possible ways here together with a pure javascript trick which works across all browsers:
// with jQuery
$(document).ready(function(){ /* ... */ });
// shorter jQuery version
$(function(){ /* ... */ });
// without jQuery (doesn't work in older IEs)
document.addEventListener('DOMContentLoaded', function(){
// your code goes here
}, false);
// and here's the trick (works everywhere)
function r(f){/in/.test(document.readyState)?setTimeout('r('+f+')',9):f()}
// use like
r(function(){
alert('DOM Ready!');
});
The trick here, as explained by the original author, is that we are checking the document.readyState property. If it contains the string in (as in uninitialized and loading, the first two DOM ready states out of 5) we set a timeout and check again. Otherwise, we execute the passed function.
And here's the jsFiddle for the trick which works across all browsers.
Thanks to Tutorialzine for including this in their book.
Tested in IE9, and latest Firefox and Chrome and also supported in IE8.
document.onreadystatechange = function () {
var state = document.readyState;
if (state == 'interactive') {
init();
} else if (state == 'complete') {
initOnCompleteLoad();
}
};
Example: http://jsfiddle.net/electricvisions/Jacck/
UPDATE - reusable version
I have just developed the following. It's a rather simplistic equivalent to jQuery or Dom ready without backwards compatibility. It probably needs further refinement. Tested in latest versions of Chrome, Firefox and IE (10/11) and should work in older browsers as commented on. I'll update if I find any issues.
window.readyHandlers = [];
window.ready = function ready(handler) {
window.readyHandlers.push(handler);
handleState();
};
window.handleState = function handleState () {
if (['interactive', 'complete'].indexOf(document.readyState) > -1) {
while(window.readyHandlers.length > 0) {
(window.readyHandlers.shift())();
}
}
};
document.onreadystatechange = window.handleState;
Usage:
ready(function () {
// your code here
});
It's written to handle async loading of JS but you might want to sync load this script first unless you're minifying. I've found it useful in development.
Modern browsers also support async loading of scripts which further enhances the experience. Support for async means multiple scripts can be downloaded simultaneously all while still rendering the page. Just watch out when depending on other scripts loaded asynchronously or use a minifier or something like browserify to handle dependencies.
The good folks at HubSpot have a resource where you can find pure Javascript methodologies for achieving a lot of jQuery goodness - including ready
http://youmightnotneedjquery.com/#ready
function ready(fn) {
if (document.readyState != 'loading'){
fn();
} else if (document.addEventListener) {
document.addEventListener('DOMContentLoaded', fn);
} else {
document.attachEvent('onreadystatechange', function() {
if (document.readyState != 'loading')
fn();
});
}
}
example inline usage:
ready(function() { alert('hello'); });
I'm not quite sure what you're asking, but maybe this can help:
window.onload = function(){
// Code. . .
}
Or:
window.onload = main;
function main(){
// Code. . .
}
Your method (placing script before the closing body tag)
<script>
myFunction()
</script>
</body>
</html>
is a reliable way to support old and new browsers.
Ready
function ready(fn){var d=document;(d.readyState=='loading')?d.addEventListener('DOMContentLoaded',fn):fn();}
Use like
ready(function(){
//some code
});
For self invoking code
(function(fn){var d=document;(d.readyState=='loading')?d.addEventListener('DOMContentLoaded',fn):fn();})(function(){
//Some Code here
//DOM is avaliable
//var h1s = document.querySelector("h1");
});
Support: IE9+
Here's a cleaned-up, non-eval-using version of Ram-swaroop's "works in all browsers" variety--works in all browsers!
function onReady(yourMethod) {
var readyStateCheckInterval = setInterval(function() {
if (document && document.readyState === 'complete') { // Or 'interactive'
clearInterval(readyStateCheckInterval);
yourMethod();
}
}, 10);
}
// use like
onReady(function() { alert('hello'); } );
It does wait an extra 10 ms to run, however, so here's a more complicated way that shouldn't:
function onReady(yourMethod) {
if (document.readyState === 'complete') { // Or also compare to 'interactive'
setTimeout(yourMethod, 1); // Schedule to run immediately
}
else {
readyStateCheckInterval = setInterval(function() {
if (document.readyState === 'complete') { // Or also compare to 'interactive'
clearInterval(readyStateCheckInterval);
yourMethod();
}
}, 10);
}
}
// Use like
onReady(function() { alert('hello'); } );
// Or
onReady(functionName);
See also How to check if DOM is ready without a framework?.
document.ondomcontentready=function(){} should do the trick, but it doesn't have full browser compatibility.
Seems like you should just use jQuery min