How to pass Array of Js functions to another Js function?

Question

I am newbie to java script. I am writing some asynchronous functions let's say func1, func2, func3. But they have to execute one after another. So i decided to use async lib to execute one after another.

SCRIPT FILE:

 function func1(param1,param2){
  //dosomething ..
 }
 function func2(param3,param4){
  //dosomething ..
 }
 function func3(param5,param6){
  //dosomething ..
 }
 function myfunction(arr){
   console.log(arr);
   async.series(arr,function(){
      //do something ..
 });
 }

HTML FILE:

<a onclick="myfunction([func1('p1','p2'),func2('p3','p4'),func('p5','p6')])"></a>

But when i try console.log, it is giving null,null,null

kindly provide me some solution regarding.

T.J. Crowder · Accepted Answer · 2016-07-28 10:07:00Z

7

You're not passing an array of function references, you're passing an array of the result of calling those functions. The array will contain whatever those functions returned (or undefined if they don't return anything).

If you want to create a function reference with arguments "baked in", you can do that with Function#bind:

myFunction([func1.bind(null, 'p1','p2'), ...])
//               ^^^^^^^^^^^^         ^

Function#bind creates a new function that, when called, will call the original with a given this value (I've used null above on the assumption this isn't important) and the arguments you give bind (followed by any arguments the new function is called with).

Example:

myfunction([
  func1.bind(null, 'p1', 'p2'),
  func1.bind(null, 'p3', 'p4'),
  func1.bind(null, 'p5', 'p6')
]);
function func1(arg1, arg2) {
  console.log("func1 got (" + arg1 + "," + arg2 + ")");
}
function myfunction(functions) {
  functions.forEach(function(f) {
    f();
  });
}

answered Jul 28, 2016 at 10:07

T.J. Crowder

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5 Comments

anil Over a year ago

Hi T.J. Crowder, Thanks for the reply ,i will try this one

Dellirium Over a year ago

In this context, when you say "followed by any arguments the new function is called with" where would those arguments be added to the above code, and would those arguments also be passed to the original function or are they just used in the new function?

T.J. Crowder Over a year ago

@Dellirium: If you do var f = foo.bind(null, 1, 2); then f(3, 4);, foo gets called with the arguments 1, 2, 3, and 4. E.g.: The ones from the bind, followed by any provided when calling the bound function. (And this in the call to foo will either be null [in strict mode] or the global object [in loose mode].)

Dellirium Over a year ago

Thanks for the clarification, one last question, if in this case we were to use foo.bind(null) and then f(1,2) would the foo get called with 1 and 2? I know it obliterates the point of the bind, but i'm curious.

T.J. Crowder Over a year ago

@Dellirium: Yes, it would. That doesn't obliterate the purpose of the bind, because it still sets a specific this, it just doesn't affect the arguments. bind is primarily used for setting this, in fact.

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