How can I call a javascript constructor using call or apply?

Question

How could I generalise the function below to take N arguments? (Using call or apply?) Is there a programmatic way to apply arguments to 'new'? I don't want the constructor to be treated like a plain function. ``` /** * This higher level function takes a constructor and arguments * and returns a function, which when called will return the * lazily constructed value. * * All the arguments, except the first are pased to the constructor. * * @param {Function} constructor */ function conthunktor(Constructor) { var args = Array.prototype.slice.call(arguments, 1); return function() { console.log(args); if (args.length === 0) { return new Constructor(); } if (args.length === 1) { return new Constructor(args[0]); } if (args.length === 2) { return new Constructor(args[0], args[1]); } if (args.length === 3) { return new Constructor(args[0], args[1], args[2]); } throw("too many arguments"); } } ``` qUnit test: ``` test("conthunktorTest", function() { function MyConstructor(arg0, arg1) { this.arg0…

Accepted Answer

Try this:

```
function conthunktor(Constructor) {
    var args = Array.prototype.slice.call(arguments, 1);
    return function() {

var Temp = function(){}, // temporary constructor
             inst, ret; // other vars

// Give the Temp constructor the Constructor's prototype
         Temp.prototype = Constructor.prototype;

// Create a new instance
         inst = new Temp;

// Call the original Constructor with the temp
         // instance as its context (i.e. its 'this' value)
         ret = Constructor.apply(inst, args);

// If an object has been returned then return it otherwise
         // return the original instance.
         // (consistent with behaviour of the new operator)
         return Object(ret) === ret ? ret : inst;

}
}
```

How can I call a javascript constructor using call or apply?

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