CODEWITHSUNDEEP
javascript
Craig Lafferty
Craig Lafferty

Reputation: 791

How do I pass a parameter back to an anonymous callback function?

I'm confused about how this works. I'm not new to javascript and I have done this before, it was just a long time ago and I have since lost the code. I don't know what this scenario is referred to, as a search for the term callbacks doesn't seem to turn up any relevant information.

1) What is this operation called? (ie: callback, passback, etc)
2) What do I do in doStuff() to pass a parameter back to the anonymous function?

Named Function/Object below

function doStuff(param1,anonymousFunction){
   //what do I do here to pass a value to 'anonymousFunction()'?
   //Can I just declare a variable?
}

FunctionCall with anonymous function as parameter below

doStuff('string', function(variableThatIWantToAccess){
   console.log(variableThatIWantToAccess);
});

Upvotes: 1

Views: 979

Answers (3)

JoshWillik
JoshWillik

Reputation: 2645

To pass data to a callback function, simply call the callback with the correct arguments.

Example

function doStuff( callback, data ){
  callback( data );
}

doStuff( alert, 'a small dog' );

working jsfiddle

Edit

The comments show that OP was wondering about jQuery.

An example of a jQuery-event-handler-like function.

function listen( eventType, callback ){
  document.addEventListener( eventType, callback );
}

Upvotes: 1

lante
lante

Reputation: 7336

Well, just:

function doStuff(param1, anonymousFunction) {
    anonymousFunction(param1 + " parameter");
}

doStuff('string', function (variableThatIWantToAccess){
   console.log(variableThatIWantToAccess); // 'string paramter'
});

AKA callback

Upvotes: 1

Wiktor Zychla
Wiktor Zychla

Reputation: 48230

function doStuff(param1,anonymousFunction){
   //what do I do here to pass a value to 'anonymousFunction()'?
   //Can I just declare a variable?

   anonymousFunction( param1 );
 }

Upvotes: 1

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