Question

I have a function that looks like this:

function SomeFunction() {

  var SomeVar;

  if (SomeCondition) {
     SomeVar = 4;
  }
}

This is equivalent to:

function SomeFunction() {

  if (SomeCondition) {
     var SomeVar = 4;
  }
}

Does using the var statement only if the condition is true make a difference or not, is there any best practice or performance implications concerning this?

Thanks.

Edit: yes, I am aware that there’s no block scope, just function scope.

Answer 1

Those are both actually equivalent. Read up on “hoisting” and “function and block scope”.

As far as speed goes, you’re better off using the second case – combining the declaration and assignment in the same statement. See: http://jsperf.com/stackoverflow-frenchie