CODEWITHSUNDEEP
javascriptclosures
Merc
Merc

Reputation: 17087

Alternative syntax for closures in Javascript: possible drawbacks?

I am still fighting my battle against my low IQ :D This is the usual infamous cycle with closures:

function r(){
  var a = [];
  var i;

  for(i=0;i<10;i++){
    a[i]=(function(x){
      return function(){return x;}
    })(i);
  return a;
}

This is quite clear to me now. In order to understand closures better, I played with the code and came up with:

function r(){
  var a = [];
  var i;
  for(i=0;i<10;i++){
    a[i] = (function(){
      var x=i;
      return function(){return x;}
    })();
  }

  return a;
}

Is my code fully equivalent?

Merc.

Upvotes: 0

Views: 169

Answers (2)

stivlo
stivlo

Reputation: 85546

I guess you didn't try them, the first one doesn't even work! Use firebug to test your code. Here is a version of the first example which actually doesn't give errors:

function r() {
    var a = [];
    var i;

    for (i=0; i<10; i++) {
        a[i] = (function (x) {
            return function () { 
                return x; 
            }
        })(i);
    }
    return a;
}

So, after adding the missing closing brace, they are equivalent, they build an array of functions that return the numbers from 0 to 9, they don't build an array of numbers from 0 to 9. So for example, calling r()[5](); returns 5 (is the sixth element of the array).

Upvotes: 2

nnnnnn
nnnnnn

Reputation: 150080

Is my code fully equivalent?

Yes.

I find it slightly easier to read the second way, because it saves having to look to the end of the immediately-executed function to find out what's passed in as a parameter (not that that's a big problem with short functions like this), but the first way is more compact and probably more common so...

Upvotes: 2

Related Questions