Develop Reference

JS Asynchron script faild to execute

I want to include an adserver js script with javascript and load it async. But every try ends with an warning and the script isn't executed.
I get the following error message:
"Failed to execute 'write' on 'Document': It isn't possible to write into a document from an asynchronously-loaded external script unless it is explicitly opened."
I have tried to following variants:
var script = document.createElement('script');
script.type = 'text/javascript';
script.src = "http://example.com/test.js";
document.body.appendChild(script);
Or I used the HTML Script attribute async
<script src="http://example.com/test.js" async></script>
But nothing worked, since the external script uses document.write. Is there another way to include such scripts?
How to "explicitly open" a page ("unless it is explicitly opened" - see warning)?

One way would be to overwrite document.write temporarily until the script is executed, afterwards replace original functionality.
var tempDocWrite = document.write;
document.write = function(el){
var div = document.createElement('div');
div.innerHTML = el;
document.body.appendChild(div)
}
var script = document.createElement('script');
script.onload = function(){
document.write = tempDocWrite
}
script.type = 'text/javascript';
script.src = "http://example.com/test.js";
document.body.appendChild(script);
note: have not tested the above code

Javascript to dynamically insert plugins and code

I'm trying to provide my users with a single <script> tag that will add some plugins to the page and execute some javascript code. I'm providing my users with a code snippet like this, and asking them to add it anywhere within the body of their website:
<script type="text/javascript" src="//my-domain/code?s=1a2b3c4d&t=faq&cb=1408412749" async></script>
In the response, I have the following Javascript code:
//add jquery to page
var script = document.createElement('script');
script.src = 'http://my-domain/assets/js/jquery.min.js';
document.body.appendChild(script);
//move jquery to our own namespace
var script = document.createElement('script');
script.innerText = "var SB = {};SB.$ = jQuery.noConflict(true);";
document.body.appendChild(script);
As you can see, I'm trying to add Jquery to the page, and then namespace it in case Jquery already exists. The problem is that when the code executes, I'm receiving this error:
Uncaught ReferenceError: jQuery is not defined
So, clearly jQuery is not loaded yet when the namespacing code executes, but I don't understand why. Shouldn't jQuery be defined at this point?

The script.onload function seems to have solved the problem:
//add jquery to page
var script = document.createElement('script');
script.src = 'http://my-domain/assets/js/jquery.min.js';
script.onload = function(){
//move jquery to our own namespace
var script = document.createElement('script');
script.innerText = "var SB = {};SB.$ = jQuery.noConflict(true);";
document.body.appendChild(script);
}
document.body.appendChild(script);

Include jQuery from another JavaScript file

I am trying to include jQuery from a javascript file. I have tried the following, although it doesn't work.
var script = '<script type="text/javascript" src="http://code.jquery.com/jquery-1.9.1.min.js"></script>';
document.getElementsByTagName('head')[0].appendChild(script);

</script> closes the opening <script> block, even if it's in a string. I would do it this way:
(function() {
var script = document.createElement('script');
script.type = 'text/javascript';
script.src = document.location.protocol + '//code.jquery.com/jquery-1.9.1.min.js';
document.getElementsByTagName('head')[0].appendChild(script)
})();

You can't have </script> anywhere inside a script block, not even inside a string, because it will end the script block there.
Break up the ending tag in the string:
var script = '<script type="text/javascript" src="http://code.jquery.com/jquery-1.9.1.min.js"></scr'+'ipt>';

Just use the jQuery getScript() method to load jQuery: http://api.jquery.com/jQuery.getScript/
...Just kidding.
Try this code:
var head = document.getElementsByTagName('head')[0];
var script = document.createElement('script');
script.type = 'text/javascript';
script.src = 'http://code.jquery.com/jquery-1.9.1.min.js';
head.appendChild(script);
From: http://unixpapa.com/js/dyna.html
Also, if using on an https page, you will need to load the script from an https compatible CDN, like the Google Hosted Libraries (src="//ajax.googleapis.com/ajax/libs/jquery/2.0.0/jquery.min.js")

(function() {
var script = document.createElement('script');
script.type = "text/javascript"; // keeping older browsers happy.
script.src = window.location.protocol + '//code.jquery.com/jquery-1.9.1.min.js';
// browsers prevent cross-protocol downloading.
(document.getElementsByTagName('head')[0] || document.getElementsByTagName('body')[0]).appendChild(script);// In Opera a site can get by without a <head>
})();

var script = document.createElement('script');
script.src = 'http://code.jquery.com/jquery-1.9.1.min.js';
document.getElementsByTagName('head')[0].appendChild(script);

using a tiny re-usable script adder:
function fetch(url){
var d=document, s='script';
d.getElementsByTagName(s)[0].parentNode.appendChild(d.createElement(s)).src=url;
}
fetch('//code.jquery.com/jquery-1.9.1.min.js');
not all pages have HEADs in all browsers, but if a script is running, so can a sibling script tag...

First of all, the variable script contains the sequence </script> which you can not make it appears as it is in your code, because browser will assume(and it must) that it is <script> tag close.
for example if your script code contains syntax error, which is a string variable that has no close " it will looks like
<script>var bad = "abcd ;</script>
to solve this you can break the </script> string like "</scr" + "ipt>" or you could escape it: "<\/script>"
so:
var script = '<script type="text/javascript" src="http://code.jquery.com/jquery-1.9.1.min.js"><\/script>';
document.getElementsByTagName('head')[0].appendChild(script);
Second thing is that appendChild() function accept a Node element and not a string
so:
var script = document.createElement("script");
script.src = "http://code.jquery.com/jquery-1.9.1.min.js";
document.getElementsByTagName("head")[0].appendChild(script);
Anyway, I prefer to use a module and JavaScript loader like RequireJS.

Can't insert js programmatically if it uses document.write

I am trying to insert js files programmatically, using jquery and something like this:
var script = document.createElement( 'script' );
script.type = 'text/javascript';
script.src = 'http://someurl/test.js';
$('body').append(script);
It works fine, if test.js contains an alert or some simple code it works fine, but if the file test.js contains document.write, and the file including the js is hosted on another domain than test.js (or localhost), nothing happens and firebug shows the error :
A call to document.write() from an asynchronously-loaded external
script was ignored.
If the test.js and the file that include it are hosted on the same domain, on chrome it still wont work but on firefox the document.write gets executed fine but the page stays "loading" forever and sniffer show request to all the files with "pending" status.
What other methods to include js files programmatically could I try?

use innerHTML instead of using document,write.
and use following code to register script,
(function() {
var jq = document.createElement('script');
jq.type = 'text/javascript';
jq.async = true;
jq.src = 'http://someurl/test.js';
var s = document.body.getElementsByTagName('script')[0];
s.parentNode.insertBefore(jq, s);
})();

Document.write is ONLY for synchronous tasks when the html is loaded (for the very first time), never for asynchronous tasks like the one you are trying to do.

What you want to do is dynamically insert a <script> DOM element into the HEAD element. I had this script sitting around. As an example, it's a race condition, but you get the idea. Call load_js with the URL. This is done for many modern APIs, and it's your best friend for cross-domain JavaScript.
<html>
<head>
<script>
var load_js = function(data, callback)
{
var head = document.getElementsByTagName("head")[0];
var script = document.createElement("script");
script.type = "text/javascript";
script.src = data;
head.appendChild(script);
if(callback != undefined)
callback();
}
load_js("http://ajax.googleapis.com/ajax/libs/jquery/1.6.2/jquery.min.js");
setTimeout(function() {
$('body').html('loaded');
}, 1000);
</script>
</head>
<body></body>
</html>

There isn't anything wrong with your approach to inserting JavaScript. document.write just sucks a little bit. It is only for synchronous tasks, so putting a document.write in a separate script file is asking for trouble. People do it anyway. The solution I've seen most often for this is to override document.write.

Reference JS file in JS file

I have a Js function that I would like to:
Reference another js file
Pull a function out.
I would like to do this JS side and not reference on the actual page as I need this process to happen dynamically.

var h = document.getElementsByTagName('head')[0],
s = document.createElement('script');
s.type = 'text/javascript';
s.onload = function () { document.getElementById('hello').innerText = h.innerText; };
s.src = 'http://html5shiv.googlecode.com/svn/trunk/html5.js';
h.appendChild(s);
see: http://jsbin.com/uhoger

If you're working with the browser, jQuery has an helper function for it, $.getScript.

The only option I can think of is to dynamically insert a new script tag into the page targeting your desired script from your initial javascript. Just have your initial script insert the new <script> tag on load, or upon request and then test for availability.