Variable leaking

[Joyston Colaco]

I have following code example
var a = b = c = d = 0;

When i run code through jsHint i get following error
 'column 23: You might be leaking a variable  here.'

Can anyone tel me what is the reason and how we can help this code?

[Morten Sjøgren]

My guess is that it's because b, c, d and d will all be declared in the global scope.

In JavaScript (unless you're running in strict-mode) if you haven't declared your variables with var before you're assigning values to them, they'll be add to the global scope.

Example:

function aFn( ) {

   a = 1;

}

console.log( a ); /// throws error, not defined yet.

aFn( );

console.log( a ); /// 1

function bFn( ) {

   window.b = 1;

}

console.log( b ); /// throws error, not defined yet.

bFn( );

console.log( b ); /// 1

function cFn( ) {

   var c = 1;

}

console.log( c ); /// throws error, not defined yet

cFn( );

console.log( c ); /// throws error, not defined yet. c is a local variable in cFn's scope.

Vars are inheriated from parent scope (closure) 

var d = 0;
function dFn( ) {

   d = 1;

}

console.log( d ); /// 0

dFn( );

console.log( c ); /// 1

As for helping you with the code:

var a = 0, b = 0, c = 0, d = 0;

Or if you most (I find this very ugly):

var a, b, c, d;