Question

If there are 2 or 3 or 20 statements using jQuery’s

$(function() { ... })

to add functions to be executed when the DOM is ready, will all those functions run in parallel or run in sequence?

Answer 1

document.ready behaves like a normal event in this respect, they happen in a sequence and in the order they were bound. You can see the relevant jQuery core source here:

This is what happens when you do $(function):

ready: function( fn ) {
    jQuery.bindReady();
    if ( jQuery.isReady ) {
        fn.call( document, jQuery );
    } else if ( readyList ) {
        readyList.push( fn );
    }
    return this;
}

And this happens later, when the “ready” event fires:

if ( readyList ) {
    var fn, i = 0;
    while ( (fn = readyList[ i++ ]) ) {
        fn.call( document, jQuery );
    }
    readyList = null;
}

If the document’s already ready, the function executes immediately, that’s the if part in the first code block above.