I'm having a (simple) issue, but I have no idea how to fix it. Essentially, every tutorial I have come across for Babylon puts all of the Javascript code inside < script > tags in the main HTML page.
However, I would like to have all of my Javascript code inside a separate file. I have tried every way of loading it as I could think of, though I am a novice at Javascript (I am decent at C++, and I can see the similarities); yet I was unable to make it load. (It works fine when called from the HTML page itself).
Does anyone know what (if anything) I can do in order to be able to load my scripts from external files, and still get everything to work? Thanks in advance!
2 options:
register to the DOMContentLoaded event in your external JS file
reference your JS file with the tag at the end of the HTML page
You can find a sample in one of my tutorials here: http://blogs.msdn.com/b/davrous/archive/2014/11/18/understanding-collisions-amp-physics-by-building-a-cool-webgl-babylon-js-demo-with-oimo-js.aspx
Enjoy and thanks for using Babylon.js! :)
David
i am new to javascript and just started small codings and sometimes running readymade codes...
Today, I used www.dynamicdrive.com Site for readymade javascript codes of which, clock and always top message is used ...
Both are working fine separately... But, when I combined both in one html page either of them is showing...
There is no names related conflicts but still this problem exists..
clock code is in same html page... while topmsg.js file is separately available which is used in html page code using tag..
Following is the error shown using Mozilla firefox.. Any body can resolve this problem of 2 javascript codes clashing...
If the problem is the scripts overwriting each other's onloads, then there's a way to avoid that.
Lets say a script does this
window.onload=someFunction;
function someFunction(){
...
}
then you can change it to
var myOldOnloadFunc = window.onload;
function someFunction(){
if(typeof(myOldOnloadFunc)=='function')myOldOnloadFunc();
...
}
You should probably do that for each script (since you don't know which is called first), just make sure you use myOldOnloadFunc for one script and myOldOnloadFunc2 for the other.
If you get stuck, seeing the associated code would help.
I see that Javascript code is normally in heading part of HTML code.
<head>
<script type="text/javascript" language="javascript" src="core.js"></script>
...
</head>
Is it OK to put the Javascript code in a body part of HTML code? I tested it, but it seems to work.
<body>
<script type="text/javascript" language="javascript" src="core.js"></script>
...
</body>
If so, why the examples of Javascript books put the javascript code in heading part?
If not, what's the difference between putting the javascript code in body/heading part?
Not only is it OK, it's actually better, since it lets the content come first.
If your viewers have a slow (eg, mobile) connection, it's better to send the actual content first, so that they can read it while the browser downloads the Javascript.
All the people saying it is better only applies if you are talking about at the bottom of the page (and that is an up for debate thing) from a code quality point of view, it is NOT ok to sprinkle script tags through your html. All references to javascript should be in a single place on the page, either the head (where they should be), or the very bottom (as a perf optimization)
Edit:
Basically, a web page is made up of 3 pieces; style (css), structure (html), and behavior (javascript). These pieces are all very distinct, so it makes sense to keep them as separate as possible. That way if you need to change some javascript, it is all in one place. If it is sprinkled through the file, it becomes much more difficult to find the code you are looking for, and that code basically becomes noise when you are just looking at structure.
It is the same arguments as why not sprinkle db access code all over your page. It has nothing to do with technical reasons, purely an architectural/design decision. Code that does different things should be kept separate for readability, maintainability, and by extension, refactorability (not sure if that last one is actually a word...)
You can do it, and people often do.
For example, people like to put their script tags just before the closing </body> to make web pages render quicker.
Also, if you do a script block after an element is created, you don't need to wait for DOM ready.
Be warned though, don't add, or remove an element from an unclosed ancestor in the markup tree (not including the script block's immediate parent element), or you will get the dreaded Operation Aborted error in IE.
Just something to add on:
I have preference of putting Javascript file right before </body>. My reasons being that:
Content can load and be shown first. If you load huge Javascript files first, which most are meaningless until the page is loaded, the user won't be able to see anything until the JS files are loaded.
Most Javascript code require to work with the UI can only run after the UI has been loaded. Placing the codes at the end of the html file reduces the need to use the onload event handler.
It is very bad habit to place Javascript snippets all over the HTML file. Placing all at the back of the HTML file allows you to manage your Javascript more efficiently.
It is legal according to the spec.
Most examples use them in the header as the headers come first and the browser will be able to parse the reference and download the JS files faster.
Additionally, these are links and are not part of the display, so traditionally, put in the header.
It is perfectly legal but there seem to be some differing opinions about it. Those who say to put all the javascript references in the head argue that the script is downloaded before the rest of the page become visible and dependent on it. So your user will not see an object on screen, attempt to interact with it and get an error because the javascript code is not yet loaded.
On the other hand, the argument goes that it takes longer to load all the script before the user sees the page and that can have a negative impact on perceived speed of your site.
JavaScripts inside body will be executed immediately while the page loads into the browser
Placing javascript at the end of the body will defer javascript load (ie: the page will render faster), but remember that any javascript function used for an event should be loaded before the event declaration, it is mainly because users may be able to fire an event before the page is completely loaded (so before the function is loaded)!
I used to put it in the head, then I've heard that it takes longer for the page to load so I started placing the scripts at the very bottom. However, I found out the most 'clean' way to do it is to place it in the head BUT you place the script inside a document.ready function. This way you have the best of both worlds. It is cleaner because it is in the head and it is not loaded before the content has been loaded, so there aren't any problems performance wise either.
With jQuery for instance, you can do it like this:
$(document).ready(function() {
alert('test');
});
The alert will only popup when the page has been fully loaded, even though the script is in the head.
I have partial control of a web page where by I can enter snippets of code at various places, but I cannot remove any preexisting code.
There is a script reference midway through the page
<script src="/unwanted.js" type="text/javascript"></script>
but I do not want the script to load. I cannot access the unwanted.js file. Is there anyway I can use javascript executing above this refernce to cause the unwanted.js file not to load?
Edit: To answer the comments asking what and why:
I'm setting up a Stack Exchange site and the WMD* js file loads halfway down the page. SE will allow you to insert HTML in various parts of the page - so you can have your custom header and footer etc. I want to override the standard WMD code with my own version of it.
I can get around the problem by just loading javascript after the original WMD script loads and replacing the functions with my own - but it would be nice not to have such a large chunk of JS load needlessly.
*WMD = the mark down editor used here at SO, and on the SE sites.
In short, you can't. Even if there is a hack, it would heavily depend on the way browsers parse the HTML and load the scripts and hence wouldn't be compatible with all browsers.
Please tell us exactly what you can and cannot do, and (preferably; this sounds fascinating) why.
If you can, try inserting <!-- before the script include and --> afterwards to comment it out.
Alternatively, look through the script file and see if there's any way that you could break it or nullify its effects. (this would depend entirely on the script itself; if you want more specific advice, please post more details, or preferably, the script itself.
Could you start an HTML comment above it and end below it in another block?
What does the contents of unwanted.js look like?
You can remove a script from the DOM after it is called by using something simple such as:
s = document.getElementById ("my_script");
s.parentNode.removeChild(s);
This will stop all functions of the script but will not take it out of user's cache. However like you wanted it can't be used.
Basically you can't unless you have access to the page content before you render it.
If you can manipulate the HTML before you send it off to the browser, you can write a regular expression that will match the desired piece of code, and remove it.
I have encountered a problem. When I use jQuery to load a page that contains heavy javascript, the page freezes. I believe it is because the js executes before the page loads as my local site does not freeze. However, $(document).ready(function(){}); seems not working with dynamically loaded pages? is that true? or anything i could do to solve this problem. Thanks a million!
$(document).ready() works fine in dynamic pages. There must be an error in your code somewhere.
The first thing to do is to try View Source and save the HTML to a plain .html file, then load that file in your browser. If that still fails then you know the problem has nothing to do with the server-side ASP/PHP/whatever code. Then try removing HTML and JavaScript piece by piece until the problem disappears. That'll help you narrow down the culprit line(s). If you can reduce your page to a small file that still demonstrates the problem, post that here and we'll try to help.
Try using
$(window).load(function(){
dosomething();
});
It will run the js after the whole page is loaded.
Avoid using
$(document).ready(function(){
dosomething();
});
It will run the js just after the loading of DOM.