Declaring Variables

[shane18]

Is there really any difference between:

 

var Age = 18;

 

or

 

Age = 18;

 

Whats the point of adding the var part? any real reason at all?

[yozyk]

Try this code

var scope = "global";
function checkscope() {
  var scope = "local";
  document.write(scope);
}
checkscope();

 

 

and this

scope = "global"; 
function checkscope() {
  scope = "local"; 
  document.write(scope); 
  myscope = "local";
  document.write(myscope); 
}
checkscope(); 
document.write(scope);
document.write(myscope);

 

 

 

http://www.mredkj.com/tutorials/reference_js_intro_ex.html

[Omirion]

Simply put when you declare a var within a function like so

 

Var foo = 1
Function myfunc(){
var foo = 0
alert(foo);
}
myfunc();
Alert(foo);

 

You are making a local var, meaning foo is only accessible throughout the execution of your function an only to it.

The result of calling myfunc() will be an alert msg with 0

The result of the alert msg outside the func will be 1.

 

If you declare your var like so

 

var foo = 1;
Function myfunc(){
foo = 0;
alert(foo);
}
myfunc();
alert(foo);

 

The result of myfunc() will be and alert with 0.

The result of calling alert(foo) outside the function will be 0.

 

This is because when creating a var like so

foo = 0

The function take the global var.

 

An when done like so

Var foo = 1

 

The function makes a foo var in local scope.

 

Google "variable scope in javascript"