DOMContentLoaded event fires when all the nodes in the page have been constructed in the DOM tree.
The load event fires when all resources such as images and sub-frames are loaded completely.DOMContentLoaded event isn't supported in IE 8 and the older versions of IE. readyState property to check if the document is loaded completely or not:const ready = function (cb) {
document.readyState === 'loading'
// The document is still loading
? document.addEventListener('DOMContentLoaded', function (e) {
cb();
})
// The document is loaded completely
: cb();
};ready function accepts a function that will be invoked when the document is ready:ready(function() {
// Do something when the document is ready
...
});