JavaScript Without jQuery

Tips and practical examples, from the CatsWhoCode post.

Listening for Document Ready
Adding Event Listeners
Selecting Elements
Using Ajax
Adding and Removing Classes
Fade In
Hiding and Showing Elements
DOM Manipulation

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
document.querySelectorAll('myParent').childNodes;

// 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 has 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);

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>';

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