How to execute a method passed as parameter to function

I too came into same scenario where I have to call the function sent as parameter to another function.

I Tried

mainfunction('callThisFunction');

First Approach

function mainFuntion(functionName)
{
    functionName();
}

But ends up in errors. So I tried

Second Approach

functionName.call(). 

Still no use. So I tried

Third Approach

this[functionName]();

which worked like a champ. So This is to just add one more way of calling. May be there may be problem with my First and Second approaches, but instead googling more and spending time I went for Third Approach.

function myfunction(param1, callbackfunction)
{
    //do processing here
   callbackfunction(); // or if you want scoped call, callbackfunction.call(scope)
}

You can just call it as a normal function:

function myfunction(param1, callbackfunction)
{
    //do processing here
    callbackfunction();
}

The only extra thing is to mention context. If you want to be able to use the this keyword within your callback, you'll have to assign it. This is frequently desirable behaviour. For instance:

function myfunction(param1, callbackfunction)
{
    //do processing here
    callbackfunction.call(param1);
}

In the callback, you can now access param1 as this. See Function.call.

object[functionName]();

object: refers to the name of the object.

functionName: is a variable whose value we will use to call a function.

by putting the variable used to refer to the function name inside the [] and the () outside the bracket we can dynamically call the object's function using the variable. Dot notation does not work because it thinks that 'functionName' is the actual name of the function and not the value that 'functionName' holds. This drove me crazy for a little bit, until I came across this site. I am glad stackoverflow.com exists <3