Convert number to characters in JavaScript

In JavaScript, converting numbers to characters is commonly done using ASCII/Unicode values. JavaScript provides the built-in String.fromCharCode() method to convert numeric values to their corresponding characters.

The String.fromCharCode() Method

The String.fromCharCode() method converts Unicode values to characters. Each number represents a specific character in the ASCII/Unicode table.

Syntax

String.fromCharCode(num1, num2, ..., numN)

Example: Single Number to Character

const n = 65;
const c = String.fromCharCode(n);
console.log(c); 
console.log("Number 72 becomes:", String.fromCharCode(72));
console.log("Number 101 becomes:", String.fromCharCode(101));

A
Number 72 becomes: H
Number 101 becomes: e

In this example, 65 corresponds to 'A', 72 to 'H', and 101 to 'e' in the ASCII table.

Converting Multiple Numbers

You can convert multiple numbers at once by passing them as separate arguments:

const result = String.fromCharCode(72, 101, 108, 108, 111);
console.log(result);

Hello

Converting an Array of Numbers

For arrays, you can use a loop or the spread operator:

// Method 1: Using for loop
const numArray = [68, 69, 70];
let chars = "";

for (let i = 0; i < numArray.length; i++) {
  chars += String.fromCharCode(numArray[i]);
}
console.log("Using loop:", chars);

// Method 2: Using spread operator
const nums = [87, 111, 114, 108, 100];
const word = String.fromCharCode(...nums);
console.log("Using spread:", word);

Using loop: DEF
Using spread: World

Common ASCII Values

Practical Example: Creating a Message

const secretCode = [74, 97, 118, 97, 83, 99, 114, 105, 112, 116];
const message = String.fromCharCode(...secretCode);
console.log("Decoded message:", message);

// Verify each character
secretCode.forEach((num, index) => {
  console.log(`${num} -> ${String.fromCharCode(num)}`);
});

Decoded message: JavaScript
74 -> J
97 -> a
118 -> v
97 -> a
83 -> S
99 -> c
114 -> r
105 -> i
112 -> p
116 -> t

Time Complexity

Converting a single number has O(1) time complexity. Converting an array of n numbers has O(n) time complexity due to iteration through the array elements.

Conclusion

Use String.fromCharCode() to convert numbers to characters in JavaScript. For multiple numbers, the spread operator provides a clean, efficient solution compared to loops.