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I'm starting to look into Javascript and JQuery (hence my choice of example below). And I found that I could define a function and call it (as expected), but that I could also just .. Do something else.. And that's the question:

function $() {
    console.log('hi');
}

$()
$

I don't get an error with either the function call or by just stating '$' without calling the function. What is the latter actually doing? And why does it work if it isn't actually calling the function?

I'm starting to look into Javascript and JQuery (hence my choice of example below). And I found that I could define a function and call it (as expected), but that I could also just .. Do something else.. And that's the question:

function $() {
    console.log('hi');
}

$()
$

I don't get an error with either the function call or by just stating '$' without calling the function. What is the latter actually doing? And why does it work if it isn't actually calling the function?

• javascript

Share Improve this question Follow edited Jan 7, 2016 at 16:26 Zach Smith asked May 28, 2015 at 22:01 Zach SmithZach Smith 8,9711515 gold badges7474 silver badges149149 bronze badges

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3 Answers 3

Sorted by: Reset to default 10

It does nothing. It's just a variable that happens to hold a function.

It's no different from the following equally useless code:

42;

A JavaScript object is a mapping between keys and values. Keys are strings and values can be anything. This makes objects a natural fit for hashmaps.

Functions are regular objects with the additional capability of being callable.

FROM https://developer.mozilla/en-US/docs/Web/JavaScript/Data_structures#.22Normal.22_objects.2C_and_functions

This mean that you can do things like:

function test(){
   console.log(1);
}

var a = test;

a();

or

var test2 = function(){
  console.log(2);
}

or autocall

//sorry for the indentation.
(
  function(){
     console.log(3);
  }
)()

Or create structures

var testHash = {
   a : 1,
   b : function(){
      console.log(4);
   }
}

testHash.b();

testHash['b']();

And create function difficult to call:

//in a browser environment
window['test3'] = function(){
   console.log(5);
} 

window['test space'] = function(){
   console.log(6);
} 

test3() //no error
test space() //error :D

---

EDIT: The user wants to know more about autocall functions:

Why this work?

(
  function(){
     console.log(3);
  }
)()

It easy to follow in 2 steps:

The parenthesis, if we know that a function is like other variables, and we know that the parenthesis is only for made groups or call functions.

var test_1 = 'string example';
var length = (test_1).length; // the same that test_1.length

Make sense in:

var test_1 = 'string';
var test_2 = ' example';
var length = (test_1 + test_2).length; // the same that test_1.length

instead of:

var test_1 = 'string';
var test_2 = ' example';
var aux = test_1 + test_2;
var length = aux.length; // the same that test_1.length

Now, Do this make sense for you?:

var length = ('string example').length; // instead the first example

Second step, we can change the string for the function.. and call it

( function(){ ... } )()

why is this interesting? Well, now appear the concept of closure.

https://developer.mozilla/en-US/docs/Web/JavaScript/Closures

The closures are a very important tool in javascript.

the name "$" is just the holder of the function, by doing the line "$" it is just to list the content of the code (in Google Chrome's developer tool).

$() is to call the function.

$ is to state what it is holding.

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