Is there a downside to not using this in JavaScript object constructors?

Question

Compare these two constructors:

A

var Person = function(name, age) {
  this.name = name;
  this.age = age;
}

B

var Person = function(name, age) {
  var o = new Object();
  o.name = name;
  o.age = age;
  return o;
}

Is there a downside to using B over A (other than brevity)?

Edit: The reason I ask is because I can learn by comparing and contrasting the two, not because I want to use B.

You waste the object that's already be constructed for you by the runtime system, for one thing. — Pointy
– Pointy, Commented Aug 22, 2014 at 22:19
yeah, B is not a constructor since it doesn't include prototype memebers in the output instance. — dandavis
– dandavis, Commented Aug 22, 2014 at 22:19
with B you might as well do var Person = {name:name,age:age}; as that is basically all you are ending up doing — Patrick Evans
– Patrick Evans, Commented Aug 22, 2014 at 22:20
B is safer when you forget to use "new " to call a constructor (since it;s not a constructor). — dandavis
– dandavis, Commented Aug 22, 2014 at 22:22

Pointy · Accepted Answer · 2014-08-22 22:23:22Z

4

One fairly important difference is that unless you take steps to deal with the issue, the returned object in B would not have the "Person" prototype.

answered Aug 22, 2014 at 22:23

Pointy

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