Question

Is there any difference between these two:

var test1 = function () {
    this.method1 = function() {}
}

and

var test2 = function() {};
test2.method1 = function() {};

Answer 1

The first snippet takes this object, whatever it is, and assigns a function to its slot (field) named method1. this can represent different objects, depending upon how test1 is called:

• when called as a standalone function — test1() — this will be window
• when called as a constructor — new test1() — this refers to the object being created
• when called via call or apply — test1.apply(someObject) — this refers to the argument

The second snippet takes the object test2 and assigns a function to its slot named method1.