Call back function basics - javascript

Question

I need to write a function:

function doTestConnCall(param1, param2, callbackfun)

param1 & param2 are parameters which I have used inside the function. The 3rd parameter - callbackfun is a function which to be called after finishing doTestConnCall

1. How to achieve this?
2. Is it possible to pass 2 callbacks inside a single method. Say doTestConnCall(param1,callback1,callback2)

Think I am missing some basics. Could any one lead me

Answer 1

You can do something like this:

callbackfun(argument1, argument2);

or:

callbackfun.apply(this, [ argument1, argument2 ]);

or:

callbackfun.call(this, argument1, argument2);

The same can be done with multiple callbacks. For example:

callback1.call(this);
callback2.call(this);

See: https://developer.mozilla.org/en-US/docs/JavaScript/Reference/Global_Objects/Function/apply

And: https://developer.mozilla.org/en-US/docs/JavaScript/Reference/Global_Objects/Function/call

Answer 2

1. Call any callback whenever appropriate in the function you are writing--in the case you described, after it completes its core work.

2. Yes, of course. Call them one after another.

    function multipleCallbacks(arg, arg, callback1, callback2) { // Do some stuff // Do error checking in the real world if you need to be tolerant callback1(); callback2(); } 

Answer 3

Functions in JS are top level constructs. That means function hello() {} is the same as var hello = function() {}; . So if you want to pass hello to the function above, you can just call doTestConnCall(param1, param2, hello) after you have defined hello() using either method above.

Answer 4

This is how you achieve it.

It is possible to pass what ever you want to as a method parameter.

function doTestConnCall(param1, param2, callbackfun){
   DO YOUR LOGIC
   callbackfun() // CALL YOUR CALLBACK
}