Javascript If-else Statement

The JavaScript if-else statement is used to execute the code whether condition is true or false. There are three forms of if statement in JavaScript.

1.if statement
2.if else statement
3.if else if statement

1.JavaScript if statement

It evaluate the content only if expression is true.

//Syntax
if(expression){  
//content to be evaluated  
}  

//Example code
<script>  
let a=20;  
if(a>10){  
document.write("value of a is greater than 10");  
}  
</script>  

//Output: value of a is greater than 10

2.Javascript if else statement

It evaluates the content whether condition is true of false.

//Syntax
if(expression){  
//content to be evaluated if condition is true  
}  
else{  
//content to be evaluated if condition is false  
}  

//Example
<script>  
let a=20;  
if(a%2==0){  
document.write("a is even number");  
}  
else{  
document.write("a is odd number");  
}  
</script>  

//Output: a is even number

3.JavaScript if else if Statement

It evaluates the content only if expression is true from several expressions.

//Syntax

if(expression1){  
//content to be evaluated if expression1 is true  
}  
else if(expression2){  
//content to be evaluated if expression2 is true  
}  
else if(expression3){  
//content to be evaluated if expression3 is true  
}  
else{  
//content to be evaluated if no expression is true  
}  

//Example

<script>  
let a=20;  
if(a==10){  
document.write("a is equal to 10");  
}  
else if(a==15){  
document.write("a is equal to 15");  
}  
else if(a==20){  
document.write("a is equal to 20");  
}  
else{  
document.write("a is not equal to 10, 15 or 20");  
}  
</script> 

//Output: a is equal to 20