JavaScript 2.0-The Complete Reference, Second ... - freecodingtutorial

fiddle(x);
document.write("After function call x ="+x+"");
At the beginning of fiddle, arg1 has a reference to the value of x:
It does not, however, have a reference to x itself. Assigning "New value" to arg1 replaces its
reference to x‘s data with a reference to a new string:
Since the assignment of "New value" isn‘t a modification of x‘s value, it is not reflected in x:
If this discussion went over your head, don‘t worry; it‘s rather advanced material. Just keep the
following rule in mind: functions passed reference types can modify but not replace values in
the calling context.
Global and Local Variables
For most JavaScript developers, there are only two basic scopes: global and local. A global
variable is one that is known (―visible‖) throughout a document, while a local variable is one
limited to the particular block of code it is defined within. The body of a function has its own
local scope. For example, in the script here, the variable x is defined globally and is available
within the function myFunction, which both prints and sets its value.
// Define x globally
var x = 5;
function myFunction()
{
document.write("Entering function");
document.write("x="+x+"");
document.write("Changing x");