- CONDITIONAL STATEMENTS:
- Conditional statements in JavaScript are used to perform different actions based on different conditions.
- Very often when you write code, you want to perform different actions for different decisions. You can use conditional statements in your code to do this.
- In JavaScript we have the following conditional statements:
- if statement - use this statement if you want to execute some code
only if a specified condition is true
- if...else statement - use this statement if you want to execute some code if the condition is true and another code if the condition is false
- if...else if....else statement - use this statement if you want to select
one of many blocks of code to be executed
- switch statement - use this statement if you want to select one of
many blocks of code to be executed
IF STATEMENT:
- You should use if statement if you want to execute some code only if a specified condition is true.
Syntax:
If <condition>
{
JavaScript code executed if condition becomes true.
}
Example:
<script language = "javascript">
var x = 5,y=6;
if (x>y)
{
document.write(' x is greater');
}
</script>
IF...ELSE STATEMENT:
- If you want to execute some code if a condition is true and another code if the condition is not true, use if....else statement.
Syntax:
if (condition)
{
Code to be executed if condition is true
}
else
{
Code to be executed if condition is not true
}
Example:
<script language = "javascript">
x = 5;
y = 6;
if (x > y)
{
document.write('x is greater');
}
else
{
document.write('y is greater');
}
</script>
- It is used when user have two or more condition to check for execution of code.
Syntax:
if <condition1>
{
Code if condition 1 is true;
}
else if <condition2>
{
Code if condition 2 is true;
}
else
{
Code if no condition becomes true;
}
Example:
<script language = "javascript">
x=5;
y=6;
z=7;
if(x>y && x>z)
{
document.write('x is greater');
}
else if(y>x && y>z)
{
document.write('y is greater');
}
else
{
document.write('z is greater');
}
</script>
SWITCH STATEMENT:
- use the switch statement to select one of many blocks of code to be executed
Syntax:
switch (n)
{
case 1:
Execute code block 1
break;
case 2:
Execute code block 2
break;
default:
Code to be executed if n is
Different from case 1 and 2
}
- First we have a single expression n (most often a variable), that is evaluated once.
- The value of the expression is then compared with the values for each case in the structure.
- If there is a match, the block of code associated with that case is executed.
- Use break to prevent the code from running into the next case automatically.
