If-3

if the variable book is "maths" then it will print as "Maths Book",  following condition will execute
else if( book == "maths" ){ document.write("Maths Book"); } 

<!DOCTYPE html>
<html>
<head>
<title>Welcome to LearnKode - A code learning platform</title>
</head>   
<body>
<script>
        
var book = "maths";

if( book == "history" ){
document.write("<b>History Book</b>");
}
else if( book == "maths" ){
document.write("<b>Maths Book</b>");
}         
else if( book == "economics" ){
document.write("<b>Economics Book</b>");
}         
else{
document.write("<b>Unknown Book</b>");
}
</script>
</body>
</html>

Output