JavaScript Control Statements – Conditional Statements
Here, we will learn Control statements – conditional statements in JavaScript.
Control Statements decide according to the condition whether a statement should be executed or not. In this post, we further go into detail about these control statements.
This post is to give a basic introduction to control statements in Javascript. At the end of this article, you will clearly understand the usage of conditional statements.
Types of Control Statements in JavaScript
- Conditional statements
- Loop /Iterative Statements
Let’s understand them with the examples:
- Conditional Statements: if, if-else, else-if ladder, switch
IF Statement
The syntax for if statement in JavaScript.
if(condition){ //block of code }
example:
<html lang="en"> <head> <title>if statement</title> <script language="javascript" type="text/javascript" > var a = window.prompt("Enter a number", "0"); a = parseInt(a); if(a<100){ document.writeln("The number is less than 100"); } </script> </head> <body> </html>
IF-ELSE Statement
The syntax for the if-else statement in JavaScript.
if(condition){ //block of code }else{ //block of code }
example:
<!doctype html> <html lang="en"> <head> <title>if-else statement</title> <script language="javascript" type="text/javascript" > var a = window.prompt("Enter a number", "0"); a = parseInt(a); var b= parseInt(prompt("Enter b number")); if(a > b) window.alert("The greatest is " +a); else alert("The greatest is " +b); </script> </head> <body> </html>
ELSE-IF Statement
The syntax for the else-if statement in JavaScript.
if(condition1){ //logic }else if(condition2){ //logic }else{ //logic }
example:
<!-- Arranging 3 numbers in order --> <!doctype html> <html lang="en"> <head> <title>nested if statement</title> </head> <body> <script language="javascript" type="text/javascript" > var a = parseInt(window.prompt("Enter Marks Sub1")); var b= parseInt(prompt("Enter Marks Sub2")); var c= parseInt(prompt("Enter Marks Sub3")); var avg=(a+b+c)/3; if(avg >= 70) alert("First With Distinction"); else if(avg >=60 && avg <70) alert("First Class"); else if(avg >=50 && avg <60) alert("Second Class"); else if(avg >=40 && avg <50) alert("Third Class"); else alert("Fail"); </script> </body> </html
SWITCH Statement
The syntax for the switch statement in JavaScript.
switch(expression) { case x: // block of code break; case y: // block of code break; default: // default block }
example:
<!-- finding the grade using switch --> <html> <head> <title> switch </title> </head> <script language="javascript" type="text/javascript"> var n1 = parseInt(window.prompt("Enter the marks in Sub1")); var n2 = parseInt(window.prompt("Enter the marks in Sub2")); var n3 = parseInt(window.prompt("Enter the marks in Sub3")); var avg= (n1+n2+n3)/3; var ch = parseInt(avg/10); //parse to int switch(ch) { case 10: case 9: case 8: case 7: window.alert("Distinction");break; case 6: window.alert("First Class");break; case 5: window.alert("Second Class");break; case 4: window.alert("Third Class ");break; default: window.alert("Fail "); } </script> </body> </html>
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