If Else in JavaScript
Branching with if
and else
in JavaScript is straightforward.
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");
}
In JavaScript, we can declare variables before conditionals, and these variables will be available in the current and all subsequent branches:
let num = 9;
if (num < 0) {
console.log(num + " is negative");
} else if (num < 10) {
console.log(num + " has 1 digit");
} else {
console.log(num + " has multiple digits");
}
To run this JavaScript code, you can save it in a file (e.g., if-else.js
) and run it using Node.js:
$ node if-else.js
7 is odd
8 is divisible by 4
either 8 or 7 are even
9 has 1 digit
Note that in JavaScript, you need parentheses around conditions, and the braces are required for multi-line blocks but optional for single-line blocks.
Unlike some languages, JavaScript does have a ternary operator (?:
), which can be used for simple conditional expressions:
let result = (5 > 3) ? "5 is greater" : "3 is greater";
console.log(result); // Outputs: 5 is greater
This can be a concise alternative to a full if-else
statement for simple conditions.