jQuery Document Ready: Tips & Practical Examples

Published on

January 21, 2020

by Jean-Baptiste Jung

Contents show

Listening for Document Ready

A page can’t be manipulated safely until the document is “ready”. For that reason, we developers have taken the habit to wrap all of our JS code inside the jQuery $(document).ready() function:

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

The same result can be achieved easily using pure JavaScript:

document.addEventListener('DOMContentLoaded', function () {
    console.log( "ready!" );
});

Adding event listeners

Event Listeners are a very important part of JavaScript development. jQuery has a very easy way to handle them:

$(someElement).on('click', function() {
    // TODO event handler logic
});

You don’t need jQuery to create event listeners in JavaScript. Here’s how to do so:

someElement.addEventListener('click', function() {
    // TODO event handler logic
});

Selecting elements

jQuery makes it super easy to select elements using an ID, a class name, tag name, etc:

// By ID
$('#myElement');

// By Class name
$('.myElement');

// By tag name
$('div');

// Children
$('#myParent').children();

// Complex selecting
$('article#first p.summary');

Pure JavaScript features various way to select elements. All of the methods below work on all modern browsers as well as IE8+.

// By ID
document.querySelector('#myElement');

// By Class name
document.querySelectorAll('.myElement');

// By tag name
document.querySelectorAll('div');

// Children
$('#myParent').children();

// Complex selecting
document.querySelectorAll('article#first p.summary');

Using Ajax

As most of you know, Ajax is a set of technologies allowing you to create asynchronymous web applications. jQuery have a set of useful methods for Ajax, including get() as shown below:

$.get( "ajax/test.html", function( data ) {
    $( ".result" ).html( data );
    alert( "Load was performed." );
});

Although jQuery makes Ajax development easier and faster, it’s a sure thing that you don’t need the framework to use Ajax:

var request = new XMLHttpRequest();
request.open('GET', 'ajax/test.html', true);

request.onload = function (e) {
    if (request.readyState === 4) {

        // Check if the get was successful.

        if (request.status === 200) {
            console.log(request.responseText);
        } else {
            console.error(request.statusText);
        }
    }
};

Adding and removing classes

If you need to add or remove an element’s class, jQuery has two dedicated methods to do so:

// Adding a class
$('#foo').addClass('bold');

// Removing a class
$('#foo').removeClass('bold');

Without jQuery, adding a class to an element is pretty easy. To remove a class, you’ll need to use the replace() method:

// Adding a class
document.getElementById('foo').className += 'bold';

// Removing a class
document.getElementById('foo').className = document.getElementById('foo').className.replace(/^bold$/, '');

Fade In

Here’s a practical example of why jQuery is so popular. Fading an element only takes a single line of code:

$(el).fadeIn();

The exact same effect can be achieved in pure JavaScript, but the code is way longer and more complicated.

function fadeIn(el) {
  el.style.opacity = 0;

  var last = +new Date();
  var tick = function() {
    el.style.opacity = +el.style.opacity + (new Date() - last) / 400;
    last = +new Date();

    if (+el.style.opacity < 1) {
      (window.requestAnimationFrame && requestAnimationFrame(tick)) || setTimeout(tick, 16);
    }
  };

  tick();
}

fadeIn(el);

Source: Stack Overflow

Hiding and showing elements

Hiding and showing elements is a very common task. jQuery offers the hide() and show() methods for modifying the display of an element.

// Hiding element
$(el).hide();

// Showing element
$(el).show();

In pure JavaScript, showing or hiding elements isn’t more complicated:

// Hiding element
el.style.display = 'none';

// Showing element
el.style.display = 'block';

DOM manipulation

Manipulating the DOM with jQuery is very easy. Let’s say you would like to append a <p> element to #container:

$("#container").append("<p>more content</p>");

Doing so in pure JavaScript isn’t much of a big deal either:

document.getElementById("container").innerHTML += "<p>more content</p>";