when does a dynamically loaded CSS into head get executed - javascript

If already answered somewhere, I would appreciate the link I just can't find it.
I load .php pages with either
<?php include 'header.php'; ?> directly or on button/link action with
<a href="#" data-toggle="modal" role="button" data-target="#genericModal" onclick="loadModalContent(\'profil.php\',\'genericModal\')">.
Some of the loaded children need the same .css & other files as their parent, so I though I would use the following code to load
function loadStyleSheet(uri){
//jquery might not be loaded yet, so do long form
var ss = document.styleSheets;
for (var i = 0, max = ss.length; i < max; i++) {
if (ss[i].href.indexOf(uri) > -1){
return;
}
}
var styleSheet = document.createElement("link");
styleSheet.href = uri;
styleSheet.rel = "stylesheet";
styleSheet.type = "text/css";
document.getElementsByTagName("head")[0].appendChild(styleSheet);
};
and then I have i.e. two files:
parent.php
<html>
<head>
<link rel="stylesheet" href="css/bootstrap.css"/>
<link....something else and more....
</head>
<body>
load in one way or another the child.php
</body>
</html>
and
child.php (no html, no head or body)
<script>
loadStyleSheet("css/bootstrap.css");
loadStyleSheet("css/child.css");
</script>
<div class="xyz">
something more here
</div>
But my question is now, how the browsers react to it. Because basically the parent already went through his <head></head> and is building the page and somewhere in the middle I tell him to load some other code and oh by the way, append a .css with javascript to his <head> (I don't have <head>s in the child files). How do browsers react to this?
I understand I probably could use loaders, but would like to avoid them for now.
I also could add all children .css into the parents, but for clarity and load on demand design would like to keep them in the children .phps
Thanks in advance!

The browser should respond to DOM changes - which would include adding a stylesheet - right away.
However, "right away" is limited because the browser runs things single-threaded, and because it needs to actually load the stylesheet (probably from a remote location).
Generally a re-render will occur when any script that modified the DOM ends. (That could mean essentially at the </script> tag for an inline script, or when the event handler returns if an event triggered the script...)
So if you were to step through with a debugger, you would see that the <link> element appears under head as soon as you execute the following line:
document.getElementsByTagName("head")[0].appendChild(styleSheet);
But the page won't have re-rendered yet.
But even when the DOM is re-rendered if the new stylesheet resource hasn't had time to load then the rendered page will not appear updated. To a user, it will appear that the stylesheet is applied at some unspecified time, no sooner than completion of the script that created the <link> element.

I would recommend to have all the css your parent and child need added at first. If you need clarity, you can split it in two files and add them both.
But if you can't perhaps you could load the style rules inside a <style> tag instead of a <link>
Of course if you put the css inside a <style> you're not taking advantage of the caching of the browser, but if you're worried about not using it, why not to load all the css in the first place
take a look at this site

I don't know if this is exactly what you're looking for, but it's a proof of concept that might work for your desired application.
<link rel="stylesheet" href="~/lib/font-awesome/css/font-awesome.css" media="none" onload="$_font_awesome_media = this; console.log($_font_awesome_media.media); $_font_awesome_media.media='all'" />
<button type="submit" onclick="$_font_awesome_media.media='none'">Send Emails</button>
The button will manipulate the media query to turn off the font-awesome.css file. You can use this technique to show the .css files you want to show inside your child modules.
Simply use the following javascript to enable it.
$_font_awesome_media.media='all'
Please take into consideration that this is probably a "hack" but, it gets the job done and in a very efficient manner. The css files will be downloaded in the background so it doesn't slow down the website from loading initially. If Javascript is disabled you will need to determine how to handle that separately.

Related

How to pass element ID variable to jQuery load function

I am fairly new to Jquery and HTML so please bear with me. I have my index.html with a call to jquery-1.9.1.min.js and I want to create a script that would load an outside html file. Index.html is a fairly long file so I want to break up the section for cleaner code and make it easier to modify.
<html class="no-js">
<main>
<section id="testLoad"></section>
</main>
<script>window.jQuery || document.write('<script src="js/vendor/jquery-1.9.1.min.js"><\/script>')</script>
<script>$("#testLoad").load("test.html #part-1"); </script>
</body>
</html>
As you can see from the code above it loads the html file fine. What I want to do is set "#part-1" as a variable so that I can call the load script again but call a different ID from another part of the file.
I would also be open to different methods aside from this load function. All I need is to call an external html file (there are about 30 different sections) so it can display that sections data. If I do it this way is there a way to create a header file so that all of these section can have access to the same style sheet?
You'd put your load function inside a named function and pass in an argument:
function loadStuff(divId) {
$("#testLoad").load("test.html #" + divId + '');
}
In your event handler you'd call it:
$(document).ready(function() {
loadStuff('someId');
});
You could also pass in the target ID in a similar manner.
As others have pointed out, this isn't the ideal way to do what's essentially client-side templating.
It seems like you want to be able to combine multiple different "partial" html files, and for this I would recommend you look into Angular which excels at exactly this.
Not sure why you are loading the JQuery js file the way you are. That really doesn't look safe.
Another thing you can do is create an "iffy" as some people call it where it is a script that is automatically called when the page is loaded.
<script>
(function (){
//code goes here
}())
</script>
This code will run when that page is loaded.

AngularJS - inject trusted code from loaded content

I've hooked up a lazy loader in Angular. It pulls in full templates and extracts key information from that full template in order to populate a partial. This full page template has script tags which load in and then register with the existing app. All of this works fine. My problem is that I'd like to remove the only use of jQuery in this approach.
The root issue is that the JS inside of something.js doesn't execute when using $element.html(), but it does execute when using $.html(), despite the script tag being placed in the DOM in both approaches.
Working code, including lazy loader and post-bootstrap registration of lazy-loaded JS:
$http.get("/path/to/file.html").success(function(response) {
// response is a full HTML page including <doctype>
var partial = getOnlyWhatWeNeed(response);
// partial is now something like: '<script type="text/javascript" src="/path/to/something.js"></script><div ng-controller="somethingCtrl">{{something}}</div>'
// i'd like the following to not rely on full jQuery.
$("#stage").html(partial);
$("#stage").html($compile(partial)($scope)); // it is necessary to do it once before compile so that the <script> tags get dropped in and executed prior to compilation.
});
I've tried what seems like the logical translation:
$element.html($compile(partial)($scope));
and the DOM is created properly, but the JS inside of the loaded <script> tag doesn't actually execute. My research suggested this was an $sce issue, so I tried:
$element.html($compile($sce.trustAsHtml(partial)($scope));
but i get the same result. the DOM is fine, but the JS doesn't actually execute and so I get undefined controller issues.
I've tried playing with $sce.JS and $sce.RESOURCE_URL but the docs didnt elaborate much so I'm not sure I know whether or not what I'm trying is even right.
I've also tried $element[0].innerHTML but I get the same result as $element.html().
Preemptive disclaimer: I can trust the incoming HTML/JS. I know it's inadvisable. This isn't my baby and it is much more complicated than I explained so please try to stay on topic so other people in this position may not have as hard of a time as I am :)
The $http.get happens in a provider, and the $element.html happens in a directive. I consolidated them to remove noise from the problem.
Jquery will find any script tags and evaluate them (either a direct eval or appending them to the head for linked scripts) when calling html(), see this answer. I'm assuming angular's jquery lite doesn't do this. You would need to effectively replicate what jquery is doing and look for script tags in the html you are appending.
Something like this (although I haven't tested it):
$http.get("/path/to/file.html").success(function(response) {
// response is a full HTML page including <doctype>
var partial = getOnlyWhatWeNeed(response);
// partial is now something like: '<script type="text/javascript" src="/path/to/something.js"></script><div ng-controller="somethingCtrl">{{something}}</div>'
var d = document.createElement('div');
d.innerHTML = partial;
var scripts = d.getElementsByTagName('script');
for (var i = 0; i < scripts.length; i++) {
document.head.appendChild(scripts[0]);
}
$("#stage").html($compile(partial)($scope)); // it is necessary to do it once before compile so that the <script> tags get dropped in and executed prior to compilation.
});
This is far from an ideal solution as it gives you no guarantee of when things are loaded and doesn't really handle dependencies across scripts. If you can control the templates it would be simpler to remove the scripts from them and load them independently.

Recommended method to locate the current script?

I am writing a script that needs to add DOM elements to the page, at the place where the script is located (widget-like approach).
What is the best way to do this?
Here are the techniques I am considering:
Include an element with an id="Locator" right above the script. Issues:
I don't like the extra markup
If I reuse the widget in the page, several elements will have the same "Locator" id. I was thinking about adding a line in the script to remove the id once used, but still...
Add an id to the script. Issues:
even though it seems to work, the id attribute is not valid for the script element
same issue as above, several elements will have the same id if I reuse the script in the page.
Use getElementsByTagName("script") and pick the last element. This has worked for me so far, it just seems a little heavy and I am not sure if it is reliable (thinking about deferred scripts)
document.write: not elegant, but seems to do the job.
[Edit] Based on the reply from idealmachine, I am thinking about one more option:
Include in the script tag an attribute, for example goal="tabify".
Use getElementsByTagName("script") to get all the scripts.
Loop through the scripts and check the goal="tabify" attribute to find my script.
Remove the goal attribute in case there's another widget in the page.
[Edit] Another idea, also inspired by the replies so far:
Use getElementsByTagName("script") to get all the scripts.
Loop through the scripts and check innerHTML to find my script.
At the end of the script, remove the script tag in case there's another widget in the page.
Out of the box : document.currentScript (not supported by IE)
I've worked for OnlyWire which provides, as their main service, a widget to put on your site.
We use the var scripts = document.getElementsByTagName("script"); var thisScript = scripts[scripts.length - 1]; trick and it seems to work pretty well. Then we use thisScript.parentNode.insertBefore(ga, thisScript); to insert whatever we want before it, in the DOM tree.
I'm not sure I understand why you consider this a "heavy" solution... it doesn't involve iteration, it's a pure cross-browser solution which integrates perfectly.
This works with multiple copies of same code on page as well as with dynamically inserted code:
<script type="text/javascript" class="to-run">
(function(self){
if (self == window) {
var script = document.querySelector('script.to-run');
script.className = '';
Function(script.innerHTML).call(script);
} else {
// Do real stuff here. self refers to current script element.
console.log(1, self);
}
})(this);
</script>
Either document.write or picking the last script element will work for synchronously loaded scripts in the majority of web pages. However, there are some options I can think of that you did not consider to allow for async loading:
Adding a div with class="Locator" before the script. HTML classes has the advantage that duplicates are not invalid. Of course, to handle the multiple widget case, you will want to change the element's class name when done adding the HTML elements so you do not add them twice. (Note that it is also possible for an element to be a member of multiple classes; it is a space-separated list.)
Checking the src of each script element can ensure that tracking code (e.g. Google Analytics legacy tracking code) and other scripts loaded at the very end of the page will not prevent your script from working properly when async loading is used. Again, to handle the multiple widget case, you may need to remove the script elements when done with them (i.e. when the desired code has been added to the page).
One final comment I will make (although you may already be aware of this) is that when coding a widget, you need to declare all your variables using var and enclose all your code within: (JSLint can help check this)
(function(){
...
})();
This has been called a "self-executing function" and will ensure that variables used in your script do not interfere with the rest of the Web page.
Whether you drop a <script> tag in or a <div class="mywidget">, you're adding something to the markup. Personally, I prefer the latter as the script itself is only added once. Too many scripts in the page body can slow down the page load time.
But if you need to add the script tag where the widget is going to be, I don't see what's wrong with using document.write() to place a div.
I just found another method that seems to answer my question:
How to access parent Iframe from javascript
Embedding the script in an iframe allows to locate it anytime, as the script always keeps a reference to its own window.
I vote this the best approach, as it'll always work no matter how many times you add the script to the page (think widget). You're welcome to comment.
What pushed me to consider iframes in the first place was an experiment I did to build a Google gadget.
In many cases this work well (hud.js is the name of the scipt):
var jsscript = document.getElementsByTagName("script");
for (var i = 0; i < jsscript.length; i++) {
var pattern = /hud.js/i;
if ( pattern.test( jsscript[i].getAttribute("src") ) )
{
var parser = document.createElement('a');
parser.href = jsscript[i].getAttribute("src");
host = parser.host;
}
}
Also you can add individual script's name inside them.
either inside some js-script
dataset['my_prefix_name'] = 'someScriptName'
or inside HTML - in the <script> tag
data-my_prefix_name='someScriptName'
and next search appropriate one by looping over document.scripts array:
... function(){
for (var i = 0, n = document.scripts.length; i < n; i++) {
var prefix = document.scripts[i].dataset['my_prefix_name']
if (prefix == 'whatYouNeed')
return prefix
}
}
I haven't had access to internet explorer since forever, but this should work pretty much everywhere:
<script src="script.js"
data-count="30"
data-headline="My headline"
onload="uniqueFunctionName(this)"
defer
></script>
and inside script.js:
window.uniqueFunctionName = function (currentScript) {
var dataset = currentScript.dataset
console.log(dataset['count'])
console.log(dataset['headline'])
}

Javascript execution order

I want to give a static javascript block of code to a html template designer, which can be:
either inline or external or both
used once or more in the html template
and each block can determine its position in the template relative to the other javascript code blocks.
An example could be image banners served using javascript. I give code to template designer who places it in two places, once for a horizontal banner in the header and once for a vertical banner. The same code runs in both blocks but knowing their positions can determine if to serve a horizontal or a vertical image banner.
Make sense?
Another example: Say you have the same 2 javascript tags in a web page calling an external script on a server. Can the server and/or scripts determine which javascript tag it belongs to?
NOTE: Can we say this is a challenge? I know that I can avoid this puzzle very easily but I come across this on a regular basis.
JavaScript code can locate all <script> elements on the page and it can probably examine the attributes and the content to check from which element it came from. But that's probably not what you want.
What you want is a piece of JavaScript which replaces tags on the page with ad banners. The usual solution is to add a special element, say a IMG, for this and give that IMG an id or a class or maybe even a custom attribute (like adtype="vertical") and then use JavaScript to locate these elements and replace the content by changing the src attribute.
For example, using jQuery, you can should your images like so:
<img src="empty.gif" width="..." height="..." class="ad" adtype="..." />
Then you can locate each image with
$('img.ad')
[EDIT] Well, the server obviously knows which script belongs into which script tag because it inserts the script. So this is a no-brainer.
If the script wants to find out where it is in the DOM, add something which it can use to identify itself, say:
<script>var id= '329573485745';
Then you can walk all script tags and check which one contains the value of the variable id.
If you call an external script, then you can do the same but you must add the ID to the script tag as you emit the HTML:
<script id="329573485745" src="..." />
Then the external script can examine the DOM and lookup the element with this id. You will want to use an UUID for this, btw.
This way, a piece of JS can locate the script tag which added itself to the page.
Best thing would probably be to make an insert once function, and then have him insert only the function call where needed.
Like this:
timescalled=0
function buildad(){
var toinsert="" //Code to generate the desired piece of HTML
document.write(toinsert)
timescalled+=1 //So you can tell how many times the function have been called
}
Now a script block calling the function can simply be inserted wherever a banner is needed
<script type="text/javascript">buildad()</script>
Thanks for the tips everyone but I'll be answering my own question.
I figured out several ways of accomplishing the task and I give you the one which works nicely and is easy to understand.
The following chunk of code relies on outputting dummy divs and jQuery.
<script>
// Unique identifier for all dummy divs
var rnd1="_0xDEFEC8ED_";
// Unique identifier for this dummy div
var rnd2=Math.floor(Math.random()*999999);
// The dummy div
var d="<div class='"+rnd1+" "+rnd2+"'></div>";
// Script which :
// Calculates index of THIS dummy div
// Total dummy divs
// Outputs to dummy div for debugging
var f1="<script>$(document).ready(function(){";
var f2="var i=$('."+rnd1+"').index($('."+rnd2+"'))+1;";
var f3="var t=$('."+rnd1+"').length;";
var f4="$('."+rnd2+"').html(i+' / '+t);";
var f5="});<\/script>";
document.write(d+f1+f2+f3+f4+f5);
</script>
Why not not just place the function call on the page instead of the entire code block? This way you can pass in a parameter to tell it what type of advertisement is needed?
BuildAd('Tower');
BuildAd('Banner');
Javascript itself has no clue of it's position in a page. You have to target a control on the page to get it's location.
I don't think it is possible for JavaScript code to know where it was loaded from. It certainly doesn't run at the point it is found, since execution isn't directly tied to the loading process (code usually runs after the whole DOM is loaded). In fact, in the case of externals, it doesn't even make sense, since only one copy of the code will be loaded no matter how many times it is encountered.
It shouldn't be the same code for each banner - there will be a parameter passed to whatever is serving the image banner which will specify the intended size.
Can you give a specific example of what you need this for?
To edit for your recent example: The simple answer is no. I could help you approach the problem from a different direction if you post details of your problem
The term "static block of code" leaves a lot of room for interpretation.
Inline scripts (e.g., ones that rely on document.write and so must be parsed and executed during the HTML parsing phase) cannot tell where they are in the DOM at runtime. You have to tell them (as in one of the first answers you got).
I think you'll probably find that you need to change your approach.
A common way to keep code and markup separate (which is useful when providing tools to HTML designers who aren't coders) is to have them use a script tag like so:
<script defer async type='text/javascript' src='pagestuff.js'></script>
...which then triggers itself when the page is loaded (using window.onload if necessary, but there are several techniques for being triggered earlier than that, which you want because window.onload doesn't trigger until the images have all loaded).
That script then looks for markers in the markup and manipulates the page accordingly. For instance (this example uses Prototype, but you can do the same with raw JavaScript, jQuery, Closure, etc.):
document.observe("dom:loaded", initPage);
function initPage() {
var verticals = $$('div.vertical');
/* ...do something with the array of "vertical" divs in `verticals`,
such as: */
var index;
for (index = 0; index < verticals.length; ++index) {
vertical.update("I'm vertical #" + index);
}
}
The designers can then have blocks on the page that are filled in by code which they flag up in a way that's normal for them (classes or attributes, etc.). The code figures out what it should do based on the classes/attributes of the blocks it finds when it runs.

Getting content of a script file using Javascript

I have the following script element in my web page:
<script src="default.js" type="text/javascript"></script>
Using JavaScript, I want to be able to retrieve the content of the script file. I know I could use an ajax request to get the data but then I am getting something from the server that I already have locally.
So what I would prefer to do is retrieve the content from the DOM (if that's possible) or something that has the same result.
Cheers
Anthony
UPDATE
I was trying to simplify the question, maybe a bad a idea, I thought this way would cause less questions.
The real situation I have is as follows, I actually have
<script type="text/html" class="jq-ItemTemplate_Approval">
...
html template that is going to be consumed by jQuery and jTemplate
...
</script>
Now this works fine but it means each time the page loads I have to send down the template as part of the HTML of the main page. So my plan was to do the following:
<script src="template.html" type="text/html"></script>
This would mean that the browser would cache the content of template.html and I would not have to send it down each time. But to do this I need to be able to get the content from the file.
Also in this case, as far as I know, requesting the content via ajax isn't going to help all that much because it has to go back to the server to get the content anyway.
If I understand you correctly, you don't want to use Ajax to load an html template text, but rather have it loaded with the rest of the page. If you control the server side, you can always include the template text in an invisible div tag that you then reference from Javascript:
<div id="template" style="display:none;">
...template text...
</div>
<script>
// pops up the template text.
alert(document.getElementById("template").innerHTML);
</script>
If you are just looking for to load the template so that you can have it cached, you can put the contents in a variable like this:
<script>
var template = "template text..";
</script>
or you can load it using ajax and store the template in a variable so it is accessible. It's pretty trivial in jquery:
var template;
$.get("template.html", function(data){
template = data;
});
unless you load a script as literal text in the page, it does not exist as text. It is interpreted by the browser and melded into the runtime, with any other scripts.
If you want the source you have to fetch it again,if with Ajax get the responseText.
It will come from the browser cache, and doesn't have to be downloaded again.
I think what you want to do is to assign a variable inside template.js. Then you have the variable available for use wherever you want in jquery. Something like:
var tpl = "<div> ... </div>"
Wouldn't this be a simpler solution to your problem? We do this in Ext JS. I think this will work for you in jQuery.
You could get the attribute of the src of the script and then use XHR to get the contents of the JS file. It's a much cleaner way of doing it IMO. e.g.:-
if(window.XMLHttpRequest) {
var xhr = new XMLHttpRequest();
xhr.onreadystatechange = function() {
if(xhr.status == 200 && xhr.readyState == 4) {
var sourceCode = xhr.responseText;
alert('The source code is:-\n'+sourceCode);
}
}
xhr.open("GET",document.getElementById('scriptID').src,true);
xhr.send(null);
}
Using an iFrame & HTML5 Local Storage
Save the templates for rendering later...
not stoked about the iFrame, but it seems to be working pretty good (haven't ran performance tests yet)
Put the iFrame on the page you want the template on (index.html)
<html>
<head>
<iframe src="mustache.Users.html" onload="this.remove();" class="hidden" id="users_template"></iframe>
</head>
</html>
Make sure the src attribute is set
hide the element until you can get rid of it after it loads
Put this body wrapper around your template (mustache.Users.html)
(don't worry it won't show up in the template)
<body onload="localStorage.setItem('users_template',this.document.body.innerHTML);">
<ul class="list-group" id="users" >
{{#users}}<li>{{name}}</li>{{/users}}
</ul>
</body>
replace 'users_template' with whatever name for your variable
the 'onload' attribute saves the template into localStorage during load
Now You can access your templates from anywhere
localStorage.getItem('users_template')
OR
window.localStorage.getItem('users_template')
What is in the JavaScript file? If it's actual code, you can run functions and reference variables in there just like you had cut and paste them into the webpage. You'll want to put the include line above any script blocks that reference it.
Is this what your looking to accomplish?
Why not use Ajax (well Ajah because its html :-))?
when the server is set up correctly and no no-cache or past expires headers are sent, the browser will cache it.
The way that most JavaScript import files work is they include a script, that immediately calls a function with a parameter of certain text, or of another function. To better illustrate, say you have your main index.html file, set it up like this:
<html>
<head>
</head>
<body>
<script>
let modules = {};
function started(moduleName, srcTxt) {
modules[moduleName] = (srcTxt) //or something similar
}
</script>
<!--now you can include other script tags, and any script tags that will be included, their source can be gotten (if set up right, see later)-->
<script src="someOtherFile.js"></script>
</body>
</html>
now make that other file, someOtherFile.js, and right away when its loaded, simply call that "started" function which should already be declared in the scope, and when thats done, then whatever text is passed, from the file, is stored in the main index.html file. You can even stringify an entire function and put it in, for example:
started("superModule", (function() {
/*
<?myCustomTemplateLanguage
<div>
{something}Entire Javascript / html template file goes here!!{/something}
</div>
?>
*/
}).toString());
now you can access the inner content of the function, and get all the text in between the comments, or better yet, then do other parsing etc, or make some other kind of parsing identifiers at the beginning and end of the comments, as shown above, and get all text in between those

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