A simple LightWeight function to defer css in your web applications or websites.
<!--Using JsDeliver CDN-->
<script src="https://cdn.jsdelivr.net/npm/defer-css"></script>
<!-- Or Using UnPkg CDN-->
<script src="https://unpkg.com/defer-css"></script>
<!-- Or Using Bundle.run-->
<script src="https://bundle.run/defer-css"></script>
You can include using require or import but defer-css does not export anything.
It sets window.deferCss && window.deferCssData
Defined styles are loaded before the link element with defer-css id in your page
<html>
<head>
<!-- Styles will be placed before this link element-->
<link id="defer-css"/>
</head>
</html>
You can change this to your custom id
<head>
<!-- Some Styles -->
<link href="....">
<link href="....">
<link href="....">
<!-- Styles will be placed before this add-css-here element-->
<link id="add-css-here"/>
</head>
Load Css using javascript
deferCss([
'style-1.min.css',
{href: 'style-2.min.css', crossorigin: 'anonymous'}
], 'add-css-here')
Adds the following styles
<link rel="stylesheet" href="style-1.min.css" crossorigin="anonymous">
<link rel="stylesheet" href="style-2.min.css" crossorigin="anonymous">
The values of the styles array can either be a url string or an object that will be used to build your link element
If the object includes an onload function, it is executed when the css file is loaded.
deferCss([
{
href: 'style-1.min.css',
onload: function() {
// do something
}
},
])
Lets say you want to mount css in multiple places.
<head>
<link id="main-css">
<style>
.some-style-before-other-css{
background: teal;
}
</style>
<link id="other-css">
</head>
deferCss(['main-css-1.css', 'main-css-2.css'], 'main-css');
deferCss([
{
href: 'other-css-1.css',
crossorigin: 'anonymous'
},
'other-css-2.css'
], 'other-css');
This will result to.
```html
<link rel="stylesheet" href="main-css-1.css">
<link rel="stylesheet" href="main-css-2.css">
<style>
.some-style-before-other-css{
background: teal;
}
</style>
<link rel="stylesheet" href="other-css-1.css">
<link rel="stylesheet" href="other-css-2.css">
The deferCssData includes details you may need.
{
// Element mounted on, default = 'defer-css'
'defer-css': {
total: Number, // total number of css defined
loaded: Number // total number of css loaded (at the moment)
}
}
<!doctype html>
<html lang="en">
<head>
<!-- Required meta tags -->
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1, shrink-to-fit=no">
<title>Defer Css Test</title>
<!-- <script src="https://cdn.jsdelivr.net/npm/defer-css"></script>-->
<script src="./index.js"></script>
<style>
/* Show Nothing until bootstrap arrives.*/
.empty {
display: none;
}
</style>
<link id="add-css-here"/>
</head>
<body>
<div class="container empty d-block">
<div class="row">
<div class="col-md-6 offset-md-3">
<div class="card shadow" style="margin-top: 20vh">
<div class="card-body text-center">
<h1>Hello, world!</h1>
<h5 class="text-primary">
Bootstrap Loaded with defer-css
</h5>
</div>
</div>
</div>
</div>
</div>
<script>
let scripts = [
'https://stackpath.bootstrapcdn.com/bootstrap/4.3.1/css/bootstrap.min.css',
// Style with onload
{
href: './app.css',
onload: function () {
console.log(this.href + ' Style Loaded!');
// value of deferCssData
console.log(deferCssData);
}
},
];
// Defer scripts
deferCss(scripts, 'add-css-here');
</script>
</body>
</html>
FAQs
ExtraSlim Javascript to Load css in your page without affecting load speed.
The npm package defer-css receives a total of 5 weekly downloads. As such, defer-css popularity was classified as not popular.
We found that defer-css demonstrated a not healthy version release cadence and project activity because the last version was released a year ago. It has 1 open source maintainer collaborating on the project.
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