How do I pass multiple arguments into a javascript callback function?

Question

Javascript code:

function doSomething(v1,v2){ //blah; }

function SomeClass(callbackFunction,callbackFuncParameters(*Array*))={
   this.callback = callbackFunction;
   this.method = function(){
       this.callback(parameters[0],parameters[1])  // *.*
   }
}

var obj = new SomeClass( doSomething, Array('v1text','v2text') );

The problem is if I change function doSomething to

function doSomething(v1,v2,v3){ //blah; }

I have to change the corresponding line (marked as //*.*) in SomeClass to

this.callback(parameters[0],parameters[1],parameters[2]);

What can be done to avoid the (*.*) line to be changed no matter how the number of 'doSomething' function's parameters is changed?

Thanks a lot!

krosenvold · Accepted Answer · 2009-01-30 07:24:10Z

25

You probably want to use the apply method

this.callback.apply(this, parameters);

The first parameter to apply indicates the value of "this" within the callback and can be set to any value.

answered Jan 30, 2009 at 7:24

krosenvold

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2 Comments

Metropolis Over a year ago

Im a little confused on how to use this functionality. What I want to do is pass a function to a callback like this - myfunction(function(myele) { //use myele }). So I am passing an anon callback function here with the myele parameter being passed to it. How would I do this with your code above?

Harshil Modi Over a year ago

jsfiddle.net/osyzc1d4/3

Marcus · Accepted Answer · 2020-06-29 21:33:19Z

2

Another way now available is to use spread syntax.

this.callback(...callbackFuncParameters)

Here it is again with the full example from the OP:

function doSomething(v1,v2) {
    console.log('doing', {v1, v2});
}

function SomeClass(callbackFunction, callbackFuncParameters) {
   this.callback = callbackFunction;
   this.method = function(){
       this.callback(...callbackFuncParameters); // spread!
   }
}

var obj = new SomeClass( doSomething, Array('v1text','v2text') );
obj.method()
// output: doing {v1: "v1text", v2: "v2text"}

answered Jun 29, 2020 at 21:33

Marcus

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