JavaScript
In this tutorial we will learn about JavaScript conditional statement If Else.
We use conditional statement to execute a piece of code if some condition is satisfied.
We use the if keyword to create an if statement.
if
Syntax:
if ( comparison ) { //some code goes here... }
In the following example we have an if statement and the code inside it is executed if the condition is satisfied.
var x = 10; console.log("x = " + x); if ( x > 0 ) { console.log("x is greater than 0"); } console.log("End of code");
In the above code we have created an if statement. We have a variable x set to 10. In the if statement we are checking if x > 0. This is true hence code inside the if block is executed.
Output:
x = 10 x is greater than 0 End of code
We use the if and else keywords to create an if/else statement.
else
if ( comparison ) { //if block code } else { //else block code }
In the following example we have an if statement and the code inside it is executed if the condition is satisfied. Otherwise, the else block is executed.
var x = 10; console.log("x = " + x); if ( x > 20 ) { console.log("x is greater than 20"); } else { console.log("x is less than 20"); } console.log("End of code");
In the above code we have created an if/else statement. We have a variable x set to 10. In the if statement we are checking if x > 20. This is false hence code inside the else block is executed.
x = 10 x is less than 20 End of code
We can combine the else and if keywords to create multiple if/else statement.
if ( comparison1 ) { //if block1 code } else if ( comparison2 ) { //if block2 code } else { //else block code }
In the following example we have multiple if/else statement.
var x = 10; console.log("x = " + x); if ( x < 0 ) { console.log("x is less than 0"); } else if ( x == 0) { console.log("x is equal to 0"); } else { console.log("x is greater than 0"); } console.log("End of code");
We can have if/else statements inside another if/else statement.
Following is an example of a nested if/else statement.
var x = 10; var y = 20; if ( x > 0 ) { if ( y > x ) { console.log("y is greater than x"); } else if ( y == x ) { console.log("y is equal to x"); } else { console.log("y is less than x"); } } else { console.log("x is not greater than zero"); }
y is greater than x