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

How to achieve this?
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

Do you mean to call javascript function from string? Take a look at this http://stackoverflow.com/questions/912596/how-to-turn-a-string-into-a-javascript-function-call — SubRed, Nov 25 '12 at 08:10

score 1 · Answer 1 · answered Nov 25 '12 at 07:21

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

score 0 · Answer 2 · edited Nov 25 '12 at 07:24

0

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

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();   
}

edited Nov 25 '12 at 07:24

Musa

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answered Nov 25 '12 at 07:22

SAJ14SAJ

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@musa Thanks for the edit, I was trying to fix it but sometimes markdown is evil. Frankly I don't see what you put in is different than what I was doing, but what can you do. – SAJ14SAJ Nov 25 '12 at 07:26

score 0 · Answer 3 · answered Nov 25 '12 at 07:23

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.

score 0 · Answer 4 · answered Nov 25 '12 at 07:23

0

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
}

answered Nov 25 '12 at 07:23

AMember

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Call back function basics - javascript

4 Answers4