Should I be using object literals or constructor functions?

Question

I am getting confused over which way I should be creating an object in javascript. It seems there are at least two ways. One is to use object literal notation while the other uses construction functions. Is there an advantage of one over the other?

Answer 1

If you don't have behaviour associated with an object (i.e. if the object is just a container for data/state), I would use an object literal.

var data = {     foo: 42,     bar: 43 }; 

Apply the KISS principle. If you don't need anything beyond a simple container of data, go with a simple literal.

If you want to add behaviour to your object, you can go with a constructor and add methods to the object during construction or give your class a prototype.

function MyData(foo, bar) {     this.foo = foo;     this.bar = bar;      this.verify = function () {         return this.foo === this.bar;     }; }  // or: MyData.prototype.verify = function () {     return this.foo === this.bar; }; 

A class like this also acts like a schema for your data object: You now have some sort of contract (through the constructor) what properties the object initializes/contains. A free literal is just an amorphous blob of data.

You might as well have an external verify function that acts on a plain old data object:

var data = {     foo: 42,     bar: 43 };  function verify(data) {     return data.foo === data.bar; } 

However, this is not favorable with regards to encapsulation: Ideally, all the data + behaviour associated with an entity should live together.