JavaScript - convert decimal number to bin, oct, hex, etc. (to any base system)

In this short article, we would like to show how to convert any decimal number to the indicated base system using JavaScript.

Quick solution:

// ONLINE-RUNNER:browser;

var dec = 123;  // decinal number
var base = 16;  // to base 16 number - to hexadecinal number

var hex = dec.toString(base);

console.log(hex);                // 7b
console.log(hex.toUpperCase());  // 7B

Custom implementation

The below function is able to convert from decimal to:

• bin (binary system),
• oct (octal systems),
• hex (hexal / hexadecimal system),
• any indicated but not greater than 36 (add more characters to the alphabet to get greater base systems).

1. Only positive input integers

// ONLINE-RUNNER:browser;

var ALPHABET = '0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ';

function convertBase(dec, base) { // add to ALPHABET more characters to get greater base
    if (dec < 0) {
        throw new Error('Negative decimal numbers are not supported.');
    }
    if (base > ALPHABET.length) {
        throw new Error('Maximal supported base value is ' + ALPHABET.length + '.');
    }
    var result = '';
    while (true) {
        var quotient = Math.floor(dec / base);
        var position = dec - base * quotient;
        result = ALPHABET[position] + result;
        if (quotient < 1) {
            break;
        }
        dec = quotient;
    }
    return result;
}



// Usage example:

//                      dec  base
console.log(convertBase(  0,  2));  // 0       (base 2)   <--- bin
console.log(convertBase(123,  2));  // 1111011 (base 2)   <--- bin
console.log(convertBase(123,  3));  // 11120   (base 3)
console.log(convertBase(123,  4));  // 1323    (base 4)
console.log(convertBase(123,  5));  // 443     (base 5)
console.log(convertBase(123,  6));  // 323     (base 6)
console.log(convertBase(123,  7));  // 234     (base 7)
console.log(convertBase(123,  8));  // 173     (base 8)   <--- oct
console.log(convertBase(123, 10));  // 123     (base 10)  <--- dec / identity
console.log(convertBase(123, 16));  // 7B      (base 16)  <--- hex
console.log(convertBase(123, 32));  // 7R      (base 32)
console.log(convertBase(123, 36));  // 3F      (base 36)
console.log(convertBase( 36, 36));  // 10      (base 36)

2. Positive and negative input integers

// ONLINE-RUNNER:browser;

var ALPHABET = '0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ';

function convertBase(dec, base) {  // add to the ALPHABET more characters to get greater base
    if (base > ALPHABET.length) {
        throw new Error('Maximal supported base value is ' + ALPHABET.length + '.');
    }
  	if (dec === 0) {
        return '0';
    }
  	var sign = '';
    var result = '';
  	if (dec < 0) {
      	dec = -dec;
        sign = '-';
    }
    while (dec > 0) {
        var quotient = Math.floor(dec / base);
        var position = dec - base * quotient;
        dec = quotient;
        result = ALPHABET[position] + result;
    }
    return sign + result;
}



// Usage example:

//                      dec  base
console.log(convertBase(   0,  2));  //  0       (base 2)   <--- bin
console.log(convertBase(-123,  2));  // -1111011 (base 2)   <--- bin
console.log(convertBase( 123,  3));  //  11120   (base 3)
console.log(convertBase(-123,  4));  // -1323    (base 4)
console.log(convertBase( 123,  5));  //  443     (base 5)
console.log(convertBase(-123,  6));  // -323     (base 6)
console.log(convertBase( 123,  7));  //  234     (base 7)
console.log(convertBase(-123,  8));  // -173     (base 8)   <--- oct
console.log(convertBase( 123, 10));  //  123     (base 10)  <--- dec / identity
console.log(convertBase(-123, 16));  // -7B      (base 16)  <--- hex
console.log(convertBase( 123, 32));  //  7R      (base 32)
console.log(convertBase(-123, 36));  // -3F      (base 36)
console.log(convertBase(  36, 36));  //  10      (base 36)