Javascript Variables and Datatypes

JAVASCRIPT VARIABLES AND DATATYPES

As with algebra, JavaScript variables are used to hold values or expressions. A variable can have a short name, like x, or a more describing name like length. A JavaScript variable can also hold a text value like in carname="Volvo".

Rules for JavaScript variable names:

Variable names are case sensitive (y and Y are two different variables) Variable names must begin with a letter or the underscore character

Example

A variable's value can change during the execution of a script. You can refer to a variable by its name to display or change its value.

Declaring (Creating) JavaScript Variables

Creating variables in JavaScript is most often referred to as "declaring" variables. You can declare JavaScript variables with the var statement:

var x;

var carname;

After the declaration shown above, the variables has no values, but you can assign values to the variables while you declare them:

var x=5;

var carname="Volvo";

Assigning Values to JavaScript Variables

You assign values to JavaScript variables with

assignment statements: x=5;

carname="Volvo";

The variable name is on the left side of the = sign, and the value you want to assign to the variable is on the right.

After the execution of the statements above, the variable x will hold the value 5, and carname will hold the value Volvo.

Assigning Values to Undeclared JavaScript Variables

If you assign values to variables that has not yet been declared, the variables will automatically be declared.These statements:

x=5;

carname="Volvo"; have the same effect as: var x=5;

var carname="Volvo";

Redeclaring JavaScript Variables

If you redeclare a JavaScript variable, it will not lose its original value. var x=5;

var x;

After the execution of the statements above, the variable x will still have the value of 5. The value of x is not reset (or cleared) when you redeclare it.

DataTypes

Numbers - are values that can be processed and calculated.

Integers

In JavaScript, you can express integers in 3 different

Specifying bases in JavaScript

NUMBER SYSTEM  NOTATION

A normal integer without a leading 0 (zero) (ie,752)

Decimal (base 10) 

Octal (base 8)        An integer with a leading 0 (zero) (ie, 056)