Last active
October 27, 2017 05:08
Star
You must be signed in to star a gist
Lazy load JS and CSS assets
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
var ASSET_TYPE = { | |
css: 'css', | |
js: 'js' | |
}; | |
function loadCss(source) { | |
return new Promise(function(resolve, reject) { | |
var link = document.createElement('link'); | |
link.type = "text/css"; | |
link.rel = "stylesheet"; | |
link.onload = function () { resolve() }; | |
link.href = source.url; | |
document.head.appendChild(link); | |
}); | |
} | |
function loadSciptTag(source) { | |
return new Promise(function(resolve, reject) { | |
var script = document.createElement('script'); | |
script.src = source.url; | |
script.async = source.async || 0; | |
script.onload = function () { resolve() }; | |
document.body.appendChild(script); | |
}); | |
} | |
function lazyLoader(asset) { | |
switch (asset.type) { | |
case ASSET_TYPE.css: | |
return loadCss(asset.source) | |
break; | |
case ASSET_TYPE.js: | |
return loadSciptTag(asset.source) | |
break; | |
default: | |
return Promise.resolve(); | |
break; | |
} | |
} | |
function loadAssets(assets) { | |
const dependencies = Array.isArray(assets) ? assets : [assets]; | |
return dependencies.map(lazyLoader); | |
} | |
// USAGE | |
const assetLoadPromises = loadAssets( | |
[{ | |
type: ASSET_TYPE.js, | |
source: { | |
url: 'https://code.jquery.com/jquery-3.2.1.slim.min.js', | |
async: 1 | |
} | |
}, | |
{ | |
type: ASSET_TYPE.css, | |
source: { | |
url: 'https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0-beta.2/css/bootstrap.min.css' | |
} | |
}] | |
); | |
// wait for all the dependencies to load | |
Promise.all(assetLoadPromises) | |
.then(function() { | |
console.log('All assets are loaded'); | |
}); |
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment