Strange Behavior On Global And Local Variable In Javascript

I tried following code: var a = 5; function x() { console.log(a); } x(); It runs as expected and prints 5. But i changed the code so the global variable a will be overwrite as

Solution 1:

This is happening because your second a variable is being 'hoisted' to the top of the function and it hides the first a. What is actually happening is this:

var a = 5;

functionx() {
  var a;
  console.log(a);
  a = 1;
}

x();

Here is an article on hoisting from adequately good for further reading on the subject.