There are pretty good docs on MDN about this topic:

• new operator
• object initializer

There is great number of differences between object literals and functions as constructors.

You can have only one instance of object literal, while using function as a constructor you can have as much as you want.

You don't have a constructor when using object literals, so if you want to initialize your object you probably want to have some function in object literal that will initialize your object (init, boostrap etc.).

Object literal's type is Object, while function as constructor is Function, which means that they have different Prototype object linked on first step in prototype chain (Function.prototype will point to Object.prototype).

For every function that you create, there is a new object created called Prototype and function is linked to it with prototype property, while when using object literal you don't get that unique prototype object, it's connected directly to Object.prototype.

For usage purposes, I personally use object literals when I want to have only one instance of that object. Good example is config object (you shouldn't have more config objects in your app). The simplest way to create singleton pattern in JavaScript is using object literals. On the other hand, I would use function as constructor if I need multiple instances of one function. Good example are domain object (User, Task etc.).

Hope that this helps a bit.

This is how I understand it (not necessarily confident that I'm right):

1. An object literal is useful when you only have one need for that object (or a single occurrence).
2. A constructor function produces independent and isolated instances of that object literal. The new keyword is somewhat of a syntactical sugar that implements a constructor function under the hood (pretty sure, but could be wrong).