Confusion with “this” object in JavaScript anonymous functions

Question

Hi I have following JavaScript code that I am trying to run. My aim is to grasp the meaning of this in different scopes and different types of invocations in Ja

Answer 1

In your second example, when you invoke the anonymous function, the parameter that is not defined (you aren't passing anything to it.) You can do this:

    newF: function()
    {
        var that = this;
        console.log(that);
        return function(that){
            console.log(that);
        }(that); // note that we are passing our 'that' in as 'that'
    }

That will keep the proper value of the variable around.

However, since you are scoping var that above, you could just remove the function parameter as well:

    newF: function()
    {
        var that = this;
        console.log(that);
        return function(){
            console.log(that);
        }(); // 'that' is referenced above.
    }

As far as why anonymous functions have window as their this: whenever you call a function without a context (i.e. somef() vs context.somef()) this will point to the window object.

You can override that and pass a this using .apply(context, argumentsArray) or .call(context, arg1, arg2, arg3) on a function. An example:

    newF: function()
    {
        console.log('Outer:', this);
        var innerF = function(){
            console.log('Inner:', this);
        };
        return innerF.apply(this,arguments);
    }