Using a global variable in javascript

Question

How do I do this?

My code is something like this:

var number = null;

function playSong(artist,title,song,id)
{
    alert('old number was: '+[number]+'');


    var number = '10';

    alert(''+[number]+'');
}

The first alert always returns 'old number was: ' and not 10. Shouldn't it return 10 on both alerts on the second function call?

Answer 1

Remove the var in front of number in your function. You are creating a local variable by

var number = 10;

what you need is just

number = 10;

Answer 2

By using var when setting number = '10', you are declaring number as a local variable each time. Try this:

var number = null;

function playSong(artist,title,song,id)
{
    alert('old number was: '+[number]+'');


    number = '10';

    alert(''+[number]+'');
}

Answer 3

The problem is that you're declaring a new variable named number inside of the function. This new variable hides the global number variable, so the line number = 10 assigns only to this new local variable.

You need to remove the var keyword from var number = 10.

Answer 4

Like in C, you need to define your variable outside of the function/method to make it global.

var number = 0;

function playSong(artist,title,song,id)
{
    alert('old number was: '+[number]+'');
    number = '10';
    alert(''+[number]+'');
}