Replacing css file on the fly (and apply the new style to the page)
I have a page which has <link> in the header that loads the CSS named light.css. I also have a file named dark.css. I want a button to swap the style of the page all together (there are 40 selectors used in css file and some do not match in two files).
How can I remove reference to light.css with JS and remove all the styles that were applied and then load dark.css and apply all the styles from that? I can't simply reset all of the elements, since some of the styles are applied through different css files and some are dynamically generated by JS. Is there a simple, yet effective way to do that without reloading the page? Vanilla JS is preferable, however I will use jQuery for later processing anyways, so jQ is also fine.
Solution 1:
You can include all the stylesheets in the document and then activate/deactivate them as needed.
In my reading of the spec, you should be able to activate an alternate stylesheet by changing its disabled property from true to false, but only Firefox seems to do this correctly.
So I think you have a few options:
Toggle rel=alternate
<link rel="stylesheet" href="main.css">
<link rel="stylesheet alternate" href="light.css" id="light" title="Light">
<link rel="stylesheet alternate" href="dark.css" id="dark" title="Dark">
<script>
function enableStylesheet (node) {
node.rel = 'stylesheet';
}
function disableStylesheet (node) {
node.rel = 'alternate stylesheet';
}
</script>
Set and toggle disabled
<link rel="stylesheet" href="main.css">
<link rel="stylesheet" href="light.css" id="light" class="alternate">
<link rel="stylesheet" href="dark.css" id="dark" class="alternate">
<script>
function enableStylesheet (node) {
node.disabled = false;
}
function disableStylesheet (node) {
node.disabled = true;
}
document
.querySelectorAll('link[rel=stylesheet].alternate')
.forEach(disableStylesheet);
</script>
Toggle media=none
<link rel="stylesheet" href="main.css">
<link rel="stylesheet" href="light.css" media="none" id="light">
<link rel="stylesheet" href="dark.css" media="none" id="dark">
<script>
function enableStylesheet (node) {
node.media = '';
}
function disableStylesheet (node) {
node.media = 'none';
}
</script>
You can select a stylesheet node with getElementById, querySelector, etc.
(Avoid the nonstandard <link disabled>. Setting HTMLLinkElement#disabled is fine though.)
Solution 2:
You can create a new link, and replace the old one with the new one. If you put it in a function, you can reuse it wherever it's needed.
The Javascript:
function changeCSS(cssFile, cssLinkIndex) {
var oldlink = document.getElementsByTagName("link").item(cssLinkIndex);
var newlink = document.createElement("link");
newlink.setAttribute("rel", "stylesheet");
newlink.setAttribute("type", "text/css");
newlink.setAttribute("href", cssFile);
document.getElementsByTagName("head").item(cssLinkIndex).replaceChild(newlink, oldlink);
}
The HTML:
<html>
<head>
<title>Changing CSS</title>
<link rel="stylesheet" type="text/css" href="positive.css"/>
</head>
<body>
<a href="#" onclick="changeCSS('positive.css', 0);">STYLE 1</a>
<a href="#" onclick="changeCSS('negative.css', 0);">STYLE 2</a>
</body>
</html>
For simplicity, I used inline javascript. In production you would want to use unobtrusive event listeners.
Solution 3:
If you set an ID on the link element
<link rel="stylesheet" id="stylesheet" href="stylesheet1.css"/>
you can target it with Javascript
document.getElementsByTagName('head')[0].getElementById('stylesheet').href='stylesheet2.css';
or just..
document.getElementById('stylesheet').href='stylesheet2.css';
Here's a more thorough example:
<head>
<script>
function setStyleSheet(url){
var stylesheet = document.getElementById("stylesheet");
stylesheet.setAttribute('href', url);
}
</script>
<link id="stylesheet" rel="stylesheet" type="text/css" href="stylesheet1.css"/>
</head>
<body>
<a onclick="setStyleSheet('stylesheet1.css')" href="#">Style 1</a>
<a onclick="setStyleSheet('stylesheet2.css')" href="#">Style 2</a>
</body>
Solution 4:
This question is pretty old but I would suggest an approach which is not mentioned here, in which you will include both the CSS files in the HTML, but the CSS will be like
light.css
/*** light.css ***/
p.main{
color: #222;
}
/*** other light CSS ***/
and dark.css will be like
/*** dark.css ***/
.dark_layout p.main{
color: #fff;
background-color: #222;
}
/*** other dark CSS ***/
basicall every selector in dark.css will be a child of .dark_layout
Then all you need to do is to change the class of body element if someone selects to change the theme of the website.
$("#changetheme").click(function(){
$("body").toggleClass("dark_layout");
});
And now all your elements will have the dark css once the user clicks on #changetheme. This is very easy to do if you are using any kind of CSS preprocessors.
You can also add CSS animations for backgrounds and colors which makes the transition highly smooth.