window.onload vs $(document).ready()

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What are the differences between ’s window.onload and ’s $(document).ready() method?

First answer

The ready event occurs after the HTML document has been loaded, while the onload event occurs later, when all content (e.g. images) also has been loaded.

The onload event is a standard event in the DOM, while the ready event is specific to jQuery. The purpose of the ready event is that it should occur as early as possible after the document has loaded, so that code that adds functionality to the elements in the page doesn’t have to wait for all content to load.

Second answer

$(document).ready() is a jQuery event. JQuery’s $(document).ready() method gets called as soon as the DOM is ready (which means that the browser has parsed the HTML and built the DOM tree). This allows you to run code as soon as the document is ready to be manipulated.

For example, if a browser supports the DOMContentLoaded event (as many non-IE browsers do), then it will fire on that event. (Note that the DOMContentLoaded event was only added to IE in IE9+.)

Two syntaxes can be used for this:

$( document ).ready(function() {
   console.log( "ready!" );
});

Or the shorthand version:

$(function() {
   console.log( "ready!" );
});

Main points for $(document).ready():

  • It will not wait for the images to be loaded.
  • Used to execute JavaScript when the DOM is completely loaded. Put event handlers here.
  • Can be used multiple times.
  • Replace $ with jQuery when you receive “$ is not defined.”
  • Not used if you want to manipulate images. Use $(window).load() instead.

window.onload() is a native JavaScript function. The window.onload() event fires when all the content on your page has loaded, including the DOM (document object model), banner ads and images. Another difference between the two is that, while we can have more than one $(document).ready() function, we can only have one onload function.

Third answer

A Windows load event fires when all the content on your page is fully loaded including the DOM (document object model) content and asynchronous JavaScript, frames and images. You can also use body onload=. Both are the same; window.onload = function(){} and <body onload="func();"> are different ways of using the same event.

jQuery $document.ready function event executes a bit earlier than window.onload and is called once the DOM(Document object model) is loaded on your page. It will not wait for the images, frames to get fully load.

Taken from the following article:
how $document.ready() is different from window.onload()

Reprint:https://stackoverflow.com/questions/3698200/window-onload-vs-document-ready
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