Lazy Load External Javascript Files

Question

I am trying to write a javascript class that loads script files as they are needed. I have most of this working. It is possible to use the library with the following Syntax:

var scriptResource = new ScriptResource('location/of/my/script.js');
scriptResource.call('methodName', arg1, arg2);

I would like to add some additional syntactic sugar so you could write

var scriptResource = new ScriptResource('location/of/my/script.js');
scriptResource.methodName(arg1, arg2);

I'm almost certain that this isnt possible but there may be an inventive solution. I guess what there need to be is some sort of methodCall event. SO the following could work

ScriptResource = function(scriptLocation)
{
    this.onMethodCall = function(methodName)
    {
        this.call(arguments);
    }
}

This code is obviously very incomplete but I hope it gives an idea of what I am trying to do

Is something like this even remotely possible?

Can we see the code for your current call() implementation - it's hard to suggest alternate solutions if we don't know how your script works... — Christoph
– Christoph, Commented Jan 9, 2009 at 12:29

BenMorel · Accepted Answer · 2014-01-04 18:11:33Z

3

There is a non standard method, __noSuchMethod__ in Firefox that does what you're looking for
have a look at
https://developer.mozilla.org/en/Core_JavaScript_1.5_Reference/Global_Objects/Object/noSuchMethod

so you could define

obj.__noSuchMethod__ = function( id, args ) {
    this[id].apply( this, args );
}

edited Jan 4, 2014 at 18:11

BenMorel

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answered Jan 9, 2009 at 11:35

meouw

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4 Comments

Christoph Over a year ago

I was going to post the same answer: +1

Jack Ryan Over a year ago

I've just about managed to get this to work. It would be nice if there was a full cross browser solution though.

meouw Over a year ago

Really not sure how cross browser it is - may work in other mozilla based browsers? I've only used it in our office which is all firefox Anyone else know? Christoph?

Christoph Over a year ago

@meouw: it's not cross browser at all (only works in Geckos); that's why I asked for your current implementation of call() so that we might look for workarounds...

Rene Saarsoo · Accepted Answer · 2009-01-09 11:31:46Z

0

If the set of method names is limited, then you could generate those methods:

var methods = ["foo", "bar", "baz"];
for (var i=0; i<methods.length; i++) {
    var method_name = methods[i];
    WildCardMethodHandler[method_name] = function () {
        this.handleAllMethods(method_name);
    };
}

edit: Posted this answer before the question changed dramatically.

edited Jan 9, 2009 at 11:31

answered Jan 9, 2009 at 11:23

Rene Saarsoo

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3 Comments

Jack Ryan Over a year ago

I'm afriad this isn't going to work. I need to call any method. I have made a big edit to show the usage I am after.

Rene Saarsoo Over a year ago

I almost thought I answered to the wrong question. You have made some truly extensive edits.

Jack Ryan Over a year ago

Yes. Sorry for the change. I thought it was best to present the question in more concrete terms. I saved edit as your saved you answer. Thanks for having a go at it though.

Guss · Accepted Answer · 2009-02-25 20:35:24Z

0

An intermediary solution might be to have syntax such as:

var extObj = ScriptResource('location/of/my/script.js');  
extObj('methodname')(arg1,arg2);

the code might look like this:

function ScriptResource(file) {
  return function(method) {
    loadExternalScript(file);
    return window[method];
  }
}

All kinds of assumptions in the code above, which I'd let you figure out yourself. The most interesting, IMHO, is - in your original implementation - how do you get the proxyied method to run synchronously and return a value? AFAIK you can only load external scripts asynchronously and handle them with an "onload" callback.

answered Feb 25, 2009 at 20:35

Guss

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1 Comment

Rene Saarsoo Over a year ago

Synchronous AJAX is definitely possible. I'm using it every day. This page explains how: hunlock.com/blogs/Snippets:_Synchronous_AJAX

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