Can JavaScript's `new` Operator Work with the `.apply()` Method?

Can the .apply() Method Be Used with the new Operator?

In JavaScript, creating an object instance using the new operator typically involves explicitly passing arguments to the constructor. However, it might be desirable to pass a variable number of arguments instead. This question explores the possibility of utilizing the .apply() method in conjunction with the new operator to achieve this flexibility.

The Challenge

Initially, one might attempt the following code:

function Something() {
    // init stuff
}
function createSomething() {
    return new Something.apply(null, arguments);
}
var s = createSomething(a, b, c); // 's' is an instance of Something

However, this approach does not function because the new operator is incompatible with the .apply() method.

Solutions

Various solutions have been proposed to overcome this limitation:

1. Matthew Crumley's Method

This solution employs an intermediary function that inherits from the target constructor:

var createSomething = (function() {
    function F(args) {
        return Something.apply(this, args);
    }
    F.prototype = Something.prototype;

    return function() {
        return new F(arguments);
    }
})();

2. Function.prototype.bind

ECMAScript5 introduces the Function.prototype.bind method, which allows partially applying functions:

function newCall(Cls) {
    return new (Function.prototype.bind.apply(Cls, arguments));
}

This can be used as follows:

var s = newCall(Something, a, b, c);

Advantages of Using Function.prototype.bind

This approach has several advantages:

• It works with all constructors, including special ones like Date.
• It can be used concisely, directly passing arguments to new.
• It preserves the original constructor's prototype.

Explanation

Function.prototype.bind creates a new function that inherits the original function's properties. By partially applying the constructor function with the desired arguments, we can then create an instance using the new keyword.

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