new Function() with variable parameters

Question

I need to create a function with variable number of parameters using new Function() constructor. Something like this:

args = [\'a\', \'b\'];
bod         


        

Answer 1

@AndyE's answer is correct if the constructor doesn't care whether you use the new keyword or not. Some functions are not as forgiving.

If you find yourself in a scenario where you need to use the new keyword and you need to send a variable number of arguments to the function, you can use this

function Foo() {
  this.numbers = [].slice.apply(arguments);
};


var args = [1,2,3,4,5]; // however many you want
var f = Object.create(Foo.prototype);
Foo.apply(f, args);

f.numbers;          // [1,2,3,4,5]
f instanceof Foo;   // true
f.constructor.name; // "Foo"

---

ES6 and beyond!

// yup, that easy
function Foo (...numbers) {
  this.numbers = numbers
}

// use Reflect.construct to call Foo constructor
const f =
  Reflect.construct (Foo, [1, 2, 3, 4, 5])

// everything else works
console.log (f.numbers)          // [1,2,3,4,5]
console.log (f instanceof Foo)   // true
console.log (f.constructor.name) // "Foo"