Javascript Structure

Javascript Structure

1. Data Types

number

var n1 = 1;
var n2 = 2.5;

string

var s = "hello";

boolean

var isNumber = true;
var isString = false;

array

var a1 = [2, 5, 6, 8];
var a2 = [4, "hello", 4.5, "good"];

2. Expression and Statement

Example 1:

n1 = 4;

Example 2:

sum = n2 + 4;

Expression = something which evaluate to a value

Example 1:

n2 + 4   // evaluate to 6.5 (assuming n2 = 2.5)

Example 2:

4 + 5   // evaluate to 9

Example 3:

3 > 2            //=> evaluate to true

Example 4:

n1 == 2          //=> evaluate to false (assuming n1 = 1)

3. Using Operator to Process Data

arithmetic (+, -)

3 + 4          //=> 7
n1 - 3         //=> -2 (assuming n1 = 1)

increment (++)

n1++           //=> 2 (assuming n1 = 1)

relational operator (e.g. < , > , == )

3 < 2          //=> false
3 > 2          //=> true
n1 == 2        //=> false (assuming n1 = 1)

assignment (=)

n1 = 3;
sum = n2 + 4;

concatenation (+)

s + 3  //=> "hello3"  (assuming s = "hello")
s + "world"    //=> "helloworld"   (assuming s = "hello")

Comparison operators
==    Is equal to
!=    Is not equal to
===   Is strictly equal to
!==   Is not strictly equal to
>     Is greater than
>=    Is greater than or equal to
<     Is less than
<=    Is less than or equal to


alert( 5 == 5 ); // This will alert "true"
alert( 5 != 6 ); // This will alert "true"
alert( 5 < 1 ); // This will alert "false"