How to create a variadic (with variable length argument list) function wrapper in JavaScript

The intention is to build a wrapper to provide a consistent method of calling native functions with variable arity on various script hosts - so that the script could be executed in a browser as well as in the Windows Script Host or other script engines.

I am aware of 3 methods of which each one has its own drawbacks.

1. eval() method:

   function wrapper () {
       var str = '';
       for (var i=0; i<arguments.lenght; i++)
           str += (str ?', ':'') + ',arguments['+i+']';
       return eval('[native_function] ('+str+')');
       }
   

2. switch() method:

   function wrapper () {
       switch (arguments.lenght) {
           case 0:
               return [native_function] (arguments[0]);
               break;
           case 1:
               return [native_function] (arguments[0], arguments[1]);
               break;
           ...
           case n:
               return [native_function] (arguments[0], arguments[1], ... arguments[n]);
           }
       }
   

3. apply() method:

   function wrapper () {
       return [native_function].apply([native_function_namespace], arguments);
       }
   

What's wrong with them you ask?

1. Well, shall we delve into all the reasons why eval() is evil? And also all the string concatenation... Not a solution to be labeled "elegant".

2. One can never know the maximum n and thus how many cases to prepare. This also would开发者_运维问答 strech the script to immense proportions and sin against the holy DRY principle.

3. The script could get executed on older (pre- JavaScript 1.3 / ECMA-262-3) engines that don't support the apply() method.

Now the question part: is there any another solution out there?

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Just use apply(). And for your antiquated execution engines, just do this

if ( 'undefined' == typeof Function.prototype.apply )
{
  Function.prototype.apply = function( context, args )
  {
    // whatever hacky way you want to implement it - i guess eval.
  }
}

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Just like the automatic 'this' variable, there is an 'arguments' variable that holds all the arguments passed in to the function. See javascript variadic.