JavaScript How to Convert Decimal to Hexadecimal

Use the JavaScript method number.toString(16) to convert a decimal number to its hexadecimal string representation.

Examples

Input255

Output"ff"

Input16

Output"10"

Input0

Output"0"

How to Think About It

To convert a decimal number to hexadecimal, think of it as changing the number base from 10 to 16. JavaScript provides a simple way to do this by converting the number to a string in base 16 using toString(16).

Algorithm

1

Get the decimal number input.

2

Call the <code>toString</code> method on the number with 16 as the argument.

3

Return the resulting string which is the hexadecimal representation.

Code

javascript

const decimalNumber = 255;
const hexString = decimalNumber.toString(16);
console.log(hexString);

Output

ff

Dry Run

Let's trace converting 255 to hexadecimal using toString(16).

1

Start with decimal number

decimalNumber = 255

2

Convert to hex string

hexString = (255).toString(16) => 'ff'

3

Output result

console.log(hexString) prints 'ff'

Decimal Number	Hexadecimal String
255	ff

Why This Works

Step 1: Using toString with base 16

The toString method converts a number to a string in the specified base, here base 16 for hexadecimal.

Step 2: Hexadecimal digits

Digits 10 to 15 are represented as letters a to f in the output string.

Step 3: Result is a string

The output is a string representing the hexadecimal number, which can be used or displayed as needed.

Alternative Approaches

Using Number.prototype.toString with uppercase

javascript

const decimalNumber = 255;
const hexString = decimalNumber.toString(16).toUpperCase();
console.log(hexString);

This method converts to uppercase hex letters (A-F) instead of lowercase.

Using parseInt and toString for string input

javascript

const decimalString = '255';
const hexString = parseInt(decimalString, 10).toString(16);
console.log(hexString);

This approach converts a decimal string to hex by parsing first, useful if input is a string.

Complexity: O(1) time, O(1) space

Time Complexity

Conversion using toString(16) is a constant time operation because it directly converts the number without loops.

Space Complexity

The space used is constant, only storing the resulting string representation.

Which Approach is Fastest?

Using toString(16) is the fastest and simplest method compared to manual conversion or parsing strings.

Approach	Time	Space	Best For
toString(16)	O(1)	O(1)	Simple and fast conversion
toString(16).toUpperCase()	O(1)	O(1)	Uppercase hex output
parseInt + toString(16)	O(1)	O(1)	When input is a decimal string