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I want to preload a JS file and a CSS file from the landing page to optimize the main site load, after the conversion in the landing. I was looking for information about this and finally tried to get this done using:
var xhr = new XMLHttpRequest();
xhr.open('GET', 'jsUrl');
xhr.send('');
xhr = new XMLHttpRequest();
xhr.open('GET', 'cssUrl');
xhr.send('');
With Firefox this great, but with Chrome it seems that the XHR calls are cached in a different cache than the css and js files. We don´t use JQuery, the landing page must be lightweight (less load, more conversion rate).
Do you have any recommendation of another way to solve the original problem? (preload components)
Do you know how to make Chrome cache these requests?
542
It works, all the time, for everyone. But, if you're not using it, and you just need to reload that one CSS or JS file occasionally in your own browser... just open it in its own tab and hit SHIFT-reload (or CTRL-F5)!
So, now how to you preload your CSS and other external resources? The answer is simpler than you think. Currently, you load CSS and JS through the link tag. So, to preload those resources, all you need is to change the rel attribute to preload and add the as=”style” attribute (or as=”script” for JavaScript).
The rel="preload" attribute value is used to preload assets. It can be applied to several file formats, including CSS, JS, fonts, images, and more. Depending on the type of file you would like to preload, the corresponding as attribute may also need to be included along with rel="preload" .
To ensure you see the latest version of a site you need to clear the cache memory. This is done by doing a force refresh by pressing both control and F5 buttons simultaneously on your keyboard (depending on your browser). Most times a simple force cache refresh won't work and you need to clear the cache by hand.
This is a tested solution in a high volume site that works.
First, to avoid a competition between the landing page resources and the preloaded resources for the bandwith you could delay the load with javascript:
var prevOnLoad=window.onload;
function onLoadPreloadComponents() {
if(prevOnLoad) {
try{
prevOnLoad();
}catch(err){
}
}
preloadSiteComponents();
}
window.onload=onLoadPreloadComponents;
This is not the way I solved this because in my use case a flash event (using the Flash to JS brigde) signals when the landing was finally loaded. But the previous code must works as well. When the load page event is fired by the browser this function will execute previous onLoad code and the preloading.
I put an empty div cointainer where the iframe will be loaded.
<div id="mainSiteComponentsContainer" style="display: none;">
</div>
And the function code is:
function preloadSiteComponents() {
try{
document.getElementById('mainSiteComponentsContainer')
.innerHTML=
"<iframe src=\"http://www-components.renxo-cdn.net/preload-site-components-data-url-scheme-version-1.2.84-css-1.0.53.html\" frameborder=\"no\" height=\"0px\" width=\"0px\"></iframe>";
}catch(err) {
}
}
As you could see, the link url to iframe is dynamic, it changes between differents plataform versions (different deployments) to avoid unwanted browser cache with a new deployments.
The HTML that will be in the iframe could be something like this (for example):
<html class=" gecko win js" xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta content="noindex,nofollow" name="robots">
<script src="http://www-components.renxo-cdn.net/scripts/lib-1.2.84.js" type="text/javascript">
<link href="http://www-components.renxo-cdn.net/styles/skin-data-url-scheme-1.0.53.css" media="all" type="text/css" rel="stylesheet">
</head>
<body> </body>
</html>
Here you could see the links to the components that I want to preload. Finally, the div cointainer will have the iframe. After the onLoad event:
<div id="mainSiteComponentsContainer" style="display: none;">
<iframe width="0px" height="0px" frameborder="no" src="http://www-components.renxo-cdn.net/preload-site-components-data-url-scheme-version-1.2.84-css-1.0.53.html">
<html class=" gecko win js" xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta content="noindex,nofollow" name="robots">
<script src="http://www-components.renxo-cdn.net/scripts/lib-1.2.84.js" type="text/javascript">
<link href="http://www-components.renxo-cdn.net/styles/skin-data-url-scheme-1.0.53.css" media="all" type="text/css" rel="stylesheet">
</head>
<body> </body>
</html>
</iframe>
</div>
You could see the working solution here.
Use Firebug to see the delayed load of this components.
156
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