Node.js by Example: If/Else

if / else blocks in JavaScript are essential for branching on conditionals.

Here’s a basic example.

 
if (7 % 2 === 0) {
    console.log("7 is even");
} else {
    console.log("7 is odd");
}

You can have an if statement without an else.

 
if (8 % 4 === 0) {
    console.log("8 is divisible by 4");
}

Logical operators like && and || are often useful in conditions.

 
if (8 % 2 === 0 || 7 % 2 === 0) {
    console.log("either 8 or 7 are even");
}

The parenthesis is always required, but the curly braces are optional for one line statements.

 
if (5 < 3)
    console.log("5 is less than 3");
else
    console.log("5 is not less than three");

JavaScript also supports ternary operations

 
let a = 9 % 2 === 0 ? "even" : "odd";
console.log(a);

The expression within the if statement does not have to be a boolean. Any truthy value will do

 
let b = "String";
if (b) {
    console.log(b, "is truthy");
} else {
    console.log(b, "is falsey");
}
 
$ node if-else.js
7 is odd
8 is divisible by 4
either 8 or 7 are even
5 is not less than three
odd
String is truthy

Next example: .

source | license