Javascript - Create instance with array of arguments

Question

I know the possibility to call a function with an array of arguments with apply(obj,args); Is there a way to use this feature when creating a new instance of a function?

I mean something like this:

function A(arg1,arg2){     var a = arg1;     var b = arg2; }  var a = new A.apply([1,2]); //create new instance using an array of arguments 

I hope you understand what i mean... ^^^

Thanks for your help!

Solved!

I got the right answer. To make the answer fit to my question:

function A(arg1,arg2) {     var a = arg1;     var b = arg2; }  var a = new (A.bind.apply(A,[A,1,2]))(); 

Answer 1

var wrapper = function(f, args) {     return function() {         f.apply(this, args);     }; };  function Constructor() {     this.foo = 4; } var o = new (wrapper(Constructor, [1,2])); alert(o.foo); 

We take a function and arguments and create a function that applies the arguments to that function with the this scope.

Then if you call it with the new keyword it passes in a new fresh this and returns it.

The important thing is the brackets

new (wrapper(Constructor, [1,2]))

Calls the new keyword on the function returned from the wrapper, where as

new wrapper(Constructor, [1,2])

Calls the new keyword on the wrapper function.

The reason it needs to be wrapped is so that this that you apply it to is set with the new keyword. A new this object needs to be created and passed into a function which means that you must call .apply(this, array) inside a function.

Live example

Alternatively you could use ES5 .bind method

var wrapper = function(f, args) {     var params = [f].concat(args);     return f.bind.apply(f, params); }; 

See example

Answer 2

with ECMAscript 5 you can:

function createInstanceWithArguments (fConstructor, aArgs) {     var foo = Object.create(fConstructor.prototype);     fConstructor.apply(foo, aArgs);     return foo; }