How to make changeable themes using CSS and JavaScript

Question

I'm pretty new to CSS and JavaScript and I was wondering if you could make a script that allows you to change what stylesheet the site uses.

Say: you had a green theme where everything is shades of green. What would you do so the user can change it to red with the press of a button?

Has anyone any idea how to do this?

Answer 1

You can set an Id to the link tag and switch the css at runtime.

HTML

<link type="text/css" rel="stylesheet" media="all" href="../green.css" id="theme_css" /> 

JS

document.getElementById('buttonID').onclick = function () {      document.getElementById('theme_css').href = '../red.css'; }; 

Quick Demo:

    $( "#datepicker" ).datepicker();  $('button').button().on('click', function () {   let linkHref = 'https://code.jquery.com/ui/1.11.4/themes/{THEME}/jquery-ui.css';  if ($('#swapTheme').prop('href').indexOf('pepper-grinder') >= 0) {     $('#swapTheme').prop('href', linkHref.replace('{THEME}', 'black-tie'));   } else {     $('#swapTheme').prop('href', linkHref.replace('{THEME}', 'pepper-grinder'));   } });

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script> <script src="https://code.jquery.com/ui/1.12.1/jquery-ui.min.js" integrity="sha256-VazP97ZCwtekAsvgPBSUwPFKdrwD3unUfSGVYrahUqU="               crossorigin="anonymous"></script> <link href="https://code.jquery.com/ui/1.11.4/themes/pepper-grinder/jquery-ui.css" id="swapTheme" rel="stylesheet"> <div id="datepicker"></div> <button style="padding: 5px 15px;"> Switch Theme </button>