Global functions in javascript

Question

I\'m new to js and trying to understand global and private functions. I understand global and local variables. But if I have an html named test.html and a 2 js

Answer 1

Anything defined in a file without any sort of wrapper will be bound to the window object. Anything bound to the window object is global.

Example:

//these are global variables
foo = 123;
var ABC = 'school';

//these are "private" variables
test = function(){
  var foo = 123
}

(function(){
  var ABC = 'school';
}).call(this);

Since global variables in every file will be part of the window object, you can access them between files. It is important when creating "private" variables you add var. This says override any global variables in the current "wrapper". If I have a global variable foo and I define it again in a function with var they will be separate.

var foo = 123;
(function(){
  var foo = 987; //this foo is separate from the above foo
}).call(this);

If you do have a "wrapper" and you want to define a global function you can do it like this:

window.foo = 123;
(function(){
  window.foo = 123;
}).call(this);

Both functions will do the same thing.

Personally, I prefer to put everything in a wrapper and only define global variables when I need them using window.

(function(){

  //all code goes here

  //define global variable
  window.foo = 123;

})call(this);