Javascript "this" pointer within nested function

In JavaScript the this object is really based on how you make your function calls.

In general there are three ways to setup the this object:

1. someThing.someFunction(arg1, arg2, argN)
2. someFunction.call(someThing, arg1, arg2, argN)
3. someFunction.apply(someThing, [arg1, arg2, argN])

In all of the above examples the this object will be someThing. Calling a function without a leading parent object will generally get you the global object which in most browsers means the window object.

Since this appears to be among the most upvoted questions of its kind, let me add, after all these years, the ES6 solution using arrow functions:

var std_obj = {
  ...
  displayMe() {
    ...
    var doSomeEffects = () => {
                        ^^^^^^^    ARROW FUNCTION    
      // In an arrow function, the 'this' pointer is interpreted lexically,
      // so it will refer to the object as desired.
      if (this.activeEffect=="fade") { }
    };
    ...    
  }
};