Avoid Render Blocking by plugins which have both css and js dependencies - javascript

I am using a jQuery plugin it has plugin.css and plugin.js as dependencies and code is in script.js. I cant have plugin.js and script.js merged because i am using plugin only on one webpage of my website.
In order to make sure plugin.css is loaded before execution of plugin.js and script.js, normally I have no option but to have plugin.css in <head> which causes render blocking(until all resources in head are loaded,
browser doesnt render html).
Normal Way: Having CSS in <head> and JS before </body>
<!DOCTYPE html>
<html>
<head>
<link rel="stylesheet" type="text/css" href="/css/plugin.css">
</head>
<body>
// content goes here
<script type='text/javascript' src='http://ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.min.js'></script>
<script src="/js/plugin.js"></script>
<script src="/js/script.js"></script>
</body>
</html>
Proposed Way: Load CSS and JS via ajax calls and inject them when all of them are loaded, using jQuery $.when promise
<!DOCTYPE html>
<html>
<head>
</head>
<body>
// content goes here
<script type='text/javascript' src='http://ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.min.js'></script>
<script class="load-plugin">
$(document).ready(function(){
var loadPlugin = {
css : $.ajax({ url: $(".jquery-plugin-css").data("src") }),
js : $.ajax({ url: $(".jquery-plugin-js").data("src")}),
};
var scriptJs = $.ajax({ url: $(".script-js").data("src") });
$.when(loadPlugin.css, loadPlugin.js, scriptJs).then(function(){
loadPlugin.css.done(function(data){
$(".jquery-plugin-css").html(data);
});
loadPlugin.js.done(function(data){
$(".jquery-plugin-js").html(data);
});
scriptJs.done(function(data){
$(".script-js").html(data);
});
});
});
</script>
<style class="jquery-plugin-css" data-src="/css/plugin.css"></style>
<script class="jquery-plugin-js" data-src="/js/plugin.js"></script>
<script class="script-js" data-src="/js/script.js"></script>
</body>
</html>
This improved my first render time from 3.4 secs to 2.4 secs and total page load time from 8.5secs to 8secs.
But this has some limitations:
Publicly hosted urls cant be used because the urls inside the plugin files like background-images inside css files if mentioned relative to their directory then the path changes after code is pasted into html.
As the injected code is not part of the source files or external scripts they cant be debugged in developer tools.
This way of lazyloading plugins has pros and equal amount of cons. Can anyone suggest is it worth it to do it this way or any better way to do things.

What I would try is:
Combine the JS files so that the dependent code is after plugin.js
Insert a script at the bottom of the page to dynamically load the CSS first and the combined JS second. If you need example code, you might look at https://github.com/filamentgroup/loadJS/ and https://github.com/filamentgroup/loadCSS/.
Using this approach, neither the CSS nor the JS blocks rendering. The CSS is appended to the DOM, so there should be no problems with relative URLs.

Related

Javascript(Jquery) executes in HTML header but not not when in an external JS file

I know this stuff has been asked before...but I am a bit confused about this still. I have my index.html file and I have a script tag linking to my external JS file. If I only have that script tag the JS does nothing, but if I copy the JS and paste it into it's own script tag in the HTML header it works just fine. There's gotta be something I'm missing with Jquery.
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<script src="jquery-3.2.0.js"></script>
<link rel="stylesheet" href="FinalProjectCss.css">
<title>Dustin Naylor - Final Project</title>
<script src="FinalProjectJS.js"></script>
<script>
$(document).ready(function(){
$(".section").click(function(){
if($(this).next().is(":hidden")) {
$(this).next().slideDown("fast");
} else{
$(this).next().hide();
}
});
});
</script>
</head>
<body>
<span class="section">Click Me</span>
<div class = "hiddenDiv">
Oh hey there.
</div>
</body>
</html>
So the code in the last script tag that is Jquery stuff is exactly copied into a separate JS file named FinalProjectJS.js. In the current state this code is in it works as desired, but when I remove that chunk of code from the html file it doesn't work....Sorry for my nubishness, I'm rather new and any help would be great! thanks!
Can you write the contents of your jquery file: FinalProjectJS.js? The syntax for calling the external file seems to be correct. So I'm thinking it might be something about the path or the jquery external file contents itself. Make sure you don't include <script> tags on that file. Here's a sample.
Another thing, last time I've worked with jquery, I can't directly see it take effect when both my files are stored locally. It had to be stored in a server first, then accessed by my PC. Only then did my jquery took effect. A dev I worked with added some text to my Google Chrome's properties (target) so that even if my file is not stored in a server, I can see jquery take effect even if both my HTML and jquery files are stored locally.
...sorry, I'm not allowed to comment yet to clarify your post.
You must add the jQuery script tag before FinalProjectJS.js for the jQuery snippet to work.
<script src="https://code.jquery.com/jquery-3.2.1.js"
integrity="sha256-DZAnKJ/6XZ9si04Hgrsxu/8s717jcIzLy3oi35EouyE="
crossorigin="anonymous">

HTML is not reading external Javascript file

I am trying to write a very simple HTML page that displays a message generated by a JS file. I am somewhat new to HTML / JS and I am certain there is something pretty simple I am missing, but I cannot for the life of me get the page to read the script. When I load the page, it is completely BLANK without any errors in the inspector.
This is the project folder structure:
-Project (folder)
--templates (folder)
----home.html
--src (folder)
----home.js
--styles (folder)
----home.css
Also, I'm pretty sure that my HTML page SEES the script, because when I remove or rename the script, I get an error in the browser's inspector telling me that it cannot find the script. So it SEES the script, it just is not running it for some reason.
Here is the code...
home.html:
<html>
<head>
<link rel="stylesheet" type="text/css" href="../styles/home.css"></link>
<script type="type/javascript" src="../src/home.js"></script>
</head>
<body>
<div id="bodytext"></div>
</body>
</html>
home.js:
(function() {
console.log("I AM READING THE SCRIPT");
document.getElementById('bodytext').innerHTML = "I AM READING THE SCRIPT";
})();
Could some generous soul out there please clue me in to what extremely simple mistake I'm making?
Thank You!
Value for type attribute should be text/javascript as follows:
<script type="text/javascript" src="../src/home.js"></script>
Your script is running before the DOM is completely done loading. If you put your <script> tag right before your closing body tag (</body>), it will run after the DOM is loaded, and you will be able to traverse the DOM like normal.
Value for type attribute should be text/javascript as follows
enter code here
ALong with this you will have to change your java script code as follows, so that script gets executed only when page is completely loaded & document object is availabe.
window.onload = function() {
console.log("I AM READING THE SCRIPT");
document.getElementById('bodytext').innerHTML = "I AM READING THE SCRIPT";
};
What worked for me was adding charset="utf-8" to my css link as well as my javascript script (for me, both did not work). Example:
<link rel="stylesheet" type="text/css" href="css/main.css" charset="utf-8"></link>
<script src="javascript/script.js" charset="utf-8"></script>

External file script is not loading

Iam using load() for loading external html file.
$("#header_section").load("header.html");
$("#sidemenu_section").load("side_menu.html");
Here, HTML file is loaded and css also loaded but script file is not loading in the page
<script src="js/utility.js"></script>
I tried to declare the above script file inside the head and inside the body. Both are not working.
Check your relative path to the utility.js file and make sure to load juery.js library before load utility.js file.
and finally try this,
<script type="text/javascript" src="${pageContext.request.contextPath}/js/utility.js"></script>
to load the utility.js file.
I think you forget to add jquery.min.js file. use below code.
<head>
<script src="http://ajax.googleapis.com/ajax/libs/jquery/1.11.3/jquery.min.js"></script>
<script src="js/utility.js"></script>
</head>
jQuery may only execute your code with the type attribute set to "text/javascript", per this bug filed a long time ago:
http://bugs.jquery.com/ticket/3733
Try this ...
<script type="text/javascript" src="http://your.cdn.com/first.js"></script>
<script type="text/javascript">
loadScript("http://your.cdn.com/second.js", function(){
//initialization code
});
</script>
The jQuery code that adds HTML to the DOM always strips out <script> tags. It runs them and then throws them away.
An exception to that behavior is when you use "$.load()" with the hack that allows you to load a fragment of a page:
$.load("http://something.com/whatever #stuff_I_want", function() { ... });
In that case, the scripts are stripped and not evaluated/run.

How to specify, different JS file for different view page in play framework?

How do we define different javascript files for different view pages in play framework??
One way is to=>
#main(title, """
#*JS CODE*#
"""{
//Template Codes
}
And in main template, use it like=>
#(title,stringJS){
<script>
#Html(stringJS)
</script>
}
But what if the JS code is to be used in not all pages but selected few, the dev can't copy the JS code in every relative view page.In my case all the javascripts are loaded on the footer, which is a seperate template.
How do we solve this problem??
Any help is appreciated, thank you!
It's described in the Common templates use cases doc , section : 'moreScripts and moreStyles equivalents'
In very short it works like this (view)
#moreScripts = {
<script type="text/javascript">alert("hello !");</script>
}
#moreStyles = {
<style>background: pink;</style>
}
#main("Title", moreScripts, moreStyles){
Html content here ...
}
and in main.scala.html start with:
#(title: String, moreScripts: Html = Html(""), moreStyles: Html = Html(""))(content: Html)
<!DOCTYPE html>
<html>
<head>
<title>#title</title>
<link rel="stylesheet" media="screen" href="#routes.Assets.at("stylesheets/main.css")">
#moreStyles
<script src="#routes.Assets.at("javascripts/jquery-1.7.1.min.js")" type="text/javascript"></script>
#moreScripts
</head>
<body>
#content
</body>
</html>
I came up with my solution,thanks to this Helpful SO post, what I did was:
#main(title, """
#*NO JS CODE, but declaration itself*#
<script src="/assets/javascripts/libs/main.js" type="text/javascript"></script>
<script src="#routes.Assets.at("javascripts/libs/main.js")" type="text/javascript"></script>//Doing this gives out errors, so I had to hardcode the "src" location
"""{
//Template Codes
}
If there is more efficient way to solve this issue, ideas are welcome, because hard-coding src isn't an efficient way of dealing with this issue, imo.

determine which js files to load in html on the fly

I am trying to set up a project which consist of htmls and javascript/ajax - jquery with many jquery plugins.
For each of many html pages, I have to use RequireJS and here is what i want..
I want to determine based on the property(return value from an ajax call) that I should load the minified files or non minified files
So I kind of need a mechanism to determine and decide (before the page load or as soon as the page starts loading) which js files I would want to load... and then go ahead with the load.
Is there a nice way to do this?
well,
take a look at this example:
the html
<!DOCTYPE html>
<html>
<head>
<title>My Sample Project</title>
<!-- data-main attribute tells require.js to load
scripts/main.js after require.js loads. -->
<script data-main="scripts/main" src="scripts/require.js"></script>
</head>
<body>
<h1>My Sample Project</h1>
</body>
</html>
scripts/main.js
$.ajax({
url: "http://server.com/fetchMeSomeData"
context: document.body,
success: function(data){
//this would be your sample callback
// you could be fetching the parameter to ask if it is debug state or not.
var isDebugSuffix = (data.isDebug)? "" : ".min";
require(["helper/util" + isDebugSuffix], function() {
//This function is called when scripts/helper/util.min.js is loaded but when the
//isDebug would be True, it would load scripts/helper/utils.js
//your other code can go here ...
});
}
});
hope this set you on your way...

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