how to understand the brackets in the last line and how to call the function

Question

How to understand the brackets in the last line and how to call the function.

I think it would be fun()(1,1,handle); if there is no (); at last but what's the (); mean?

var handle = function(boolean){
  alert(boolean);
}

var fun = function(){
  // Some definition
  // Some function
  
  return function(a,b,handle) {
    // Some process
    if (a == b) {
      handle(true);
    } else {
      handle(false);
    }
  }
}();

[IIFE (Immediately Invoked Function Expression)](https://developer.mozilla.org/en-US/docs/Glossary/IIFE) — Reyno, Apr 15 '21 at 13:21
"*I think it would be `fun()(1,1,handle);` if there is no `()` at last*" - yes, that is correct. But we normally want `fun(1,2,handle)`. — Bergi, Apr 15 '21 at 13:46

Ashishssoni · Accepted Answer · 2021-04-15T13:44:03.570

Its immediately invoked function expression, you can learn about it here.

It is used cause the function becomes a function expression which is immediately executed. The variable within the expression can not be accessed from outside it.

like this fun immediately executed. for eg:

function greatings() {
  console.log('Welcome to GFG!')
}
// Execution of Regular Function.
greatings();
// IIFE creation and execution.
(function () {
  console.log('Welcome to GFG! in IIFE')
})()

And for your question, the () is to invoke your function and you will call the function as fun(1,1,handle) like:

var handle = function (boolean) {
  console.log('coming here')
}

var fun = (function () {
  // Some definition
  // Some function

  return function (a, b, handle) {
    // Some process
    if (a === b) {
      handle(true)
    } else {
      handle(false)
    }
  }
})()

fun(1, 1, handle)

how to understand the brackets in the last line and how to call the function

1 Answers1