Global and Local and Private Functions (Javascript)

Question

I am currently reading a book on Javascript by Pragmatic, and I\'m confused about one thing. They have a section on how to make variables global, local, or private.

Answer 1

What is the difference between local and private variables? Is there one?

Depends in which context they are used. Generally they mean the same thing. From the OOP perspective, a local variables is usually called private.

How does one make a variable global or local, They said something about putting 'var =' before it, but it was very vague.

When you put var before variable, it becomes local variables, in the absence though, it becomes global variable. For example:

var foo = 1; // local
foo = 1; // global equivalent to window.foo = 1 becomes part of window object

More Practical Example:

function myfunc(){
  var foo = 1; // presence of var keyword
  bar = 2;     // absence of var keyword
}

alert(foo); // error eg undefined
alert(bar); // 2 because bar is part of window global object