Is this function similar to a constructor?

Question

function catRecord(name, birthdate, mother) {
  return {name: name, birth: birthdate, mother: mother};
}

My understanding of a constructor is a function is used to build up the object.

Would this catRecord function count as a constructor?

Answer 1

No, the function you've given returns a new associative array with no type information. The constructor you're after is something like this:

function fixedCatRecord(name, birthdate, mother) {
    this.name = name;
    this.birthdate = birthdate;
    this.mother = mother;
}

This way, you'll have an object that knows it's a fixedCatRecord, which means it has access to all the appropriate metadata (such as knowing what methods you can call on it).

Mind you, both of them CAN be used with "new", but it will be an object of type Object (which is the default for an associative array), not an object of type catRecord.

e.g., if you're using something (like Chrome) where console.log gives type information:

// this is an Object, not what you want!
console.log(new catRecord("Fluffy", "12/12/12", "Melody"));
// this is a fixedCatRecord, good!
console.log(new fixedCatRecord("Fluffy", "12/12/12", "Melody"));

Answer 2

Would this catRecord function count as a constructor?

Nope.

It's very similar to a constructor, yes, but I wouldn't call all functions/methods that return an object "constructor". I use the term factory instead when no inheritance is involved.

The EcmaScript specification defines a constructor simply as a

Function object that creates and initialises objects.

though there's already a note on prototypical inheritance right below it. And in the language overview it says

A constructor is a function that has a property named “prototype” that is used to implement prototype-based inheritance and shared properties.

So while technically every object that implements [[construct]] is a constructor, in JavaScript the term "constructor" is used only for functions that are intended to be used with the new keyword and create instances which share a common prototype (forming a "class"). Conventionally, their names are capitalized then.