Javascript模块声明 - 性能

Question

I am trying to decide between the following ways of writing JS module. What are the implications of writing a module on Memory and CPU. Will the 2nd one take up more Memory in the browser ?

Using function declaration

function MyModule () {
    this.getOperation1 =  operation1;
    function operation1() {
        return "XYZ"
    }
}

Using variable definition

 var MyModule = {
     getOperation1: function() {
        return "XYZ"
     }
  }

Answer 1

Memory wise they're about the same - both create a single object.

However:

1. You can only use new with the function based module format. The latter just creates a single object, not a constructor that can be used to create additional instances.

2. With a function you can enclose private local variables in the scope.

However, in most cases a better approach is this:

function MyModule () {
}

MyModule.prototype.getOperation1 = function() {
    ...
}

which ensures that if you create multiple instances they all only share one copy of the getOperation1 function.

That said, if all you're trying to do is namespace the functions, and they don't naturally form an "object' (in the OOP sense) then you might just as well use the object literal syntax.

Answer 2

Refer this yui-blog for memory related argument

From the same

By using new to invoke the function, the object holds onto a worthless prototype object. That wastes memory with no offsetting advantage. If we do not use the new, we don't keep the wasted prototype object in the chain

As mentioned by @Alnitak make use of prototype object incase you are up to implement constructor function so that all instances would share the same object.

To check CPU wise [speed] use www.jsperf.com and do a performance test. Some already available tests Function Invocation , Object.create vs new , Generic