Import JavaScript file in JavaScript function [duplicate]

Question

Possible Duplicates: Include a JavaScript file in a JavaScript file How to include a JavaScript file in another JavaScript file?

What is the best way to import a JavaScript file, for example file.js, in a JavaScript function()?

For example, what is the best way to replace the todo statement:

function doSomething() {
   if (xy.doSomething == undefined) {
      // TODO: load 'oldVersionPatch.js'
   }
   ...
}

Possibly the best solution is to create script element and add it into the HTML page.

• Is it better to add/append it into head, or body (what will load when)?
• Is it better to use JavaScript or jQuery (what is more cross-browser compatible)?

Answer 1

http://api.jquery.com/jQuery.getScript/

or

(function(){
  this.__defineGetter__("__FILE__", function() {
    return (new Error).stack.split("\n")[2].split("@")[1].split(":").slice(0,-1).join(":");
  });
})();

(function(){
  this.__defineGetter__("__DIR__", function() {
    return __FILE__.substring(0, __FILE__.lastIndexOf('/'));
  });
})();

function include(file,charset) {
    if (document.createElement && document.getElementsByTagName) {
        var head = document.getElementsByTagName('head')[0];
        var script = document.createElement('script');
        script.setAttribute('type', 'text/javascript');
        script.setAttribute('src', __DIR__ + '/' + file);
        if(charset){
            script.setAttribute('charset', charset);
        }
        head.appendChild(script);
    }
}

Answer 2

  var filename = 'oldVersionPatch.js';
  var js = document.createElement('script');
  js.setAttribute("type","text/javascript");
  js.setAttribute("src", filename);
  document.getElementsByTagName("head")[0].appendChild(js);

.. should do it

Answer 3

Very simply, in JavaScript create a <script> element, append the src attribute with whatever the URL is and attach to the DOM. That should do it.

Answer 4

You have to make your code asynchronous to gain this:

var script = document.createElement('script');
script.type = 'text/javascript';
script.src = yourJavascriptFileLocation;
script.onload = script.onreadystatechange = function() {
    if (!script.readyState || script.readyState === 'complete') {
        /* Your code rely on this JavaScript code */
    }
};
var head = document.getElementsByTagName('head')[0];
// Don't use appendChild
head.insertBefore(script, head.firstChild);