JavaScript Anti-patterns Chaining assignments in var declarations.
Example
Chaining assignments as part of a var declaration will create global variables unintentionally.
For example:
(function foo() {
var a = b = 0;
})()
console.log('a: ' + a);
console.log('b: ' + b);
Will result in:
Uncaught ReferenceError: a is not defined
'b: 0'
In the above example, a is local but b becomes global. This is because of the right to left evaluation of the = operator. So the above code actually evaluated as
var a = (b = 0);
The correct way to chain var assignments is:
var a, b;
a = b = 0;
Or:
var a = 0, b = a;
This will make sure that both a and b will be local variables.
