convert number to words in JavaScript [with explanation]

Abhi
2 min readJan 9, 2023
// Define an object that maps numbers to their word form
const numbersToWords = {
0: "zero",
1: "one",
2: "two",
3: "three",
4: "four",
5: "five",
6: "six",
7: "seven",
8: "eight",
9: "nine",
10: "ten",
11: "eleven",
12: "twelve",
13: "thirteen",
14: "fourteen",
15: "fifteen",
16: "sixteen",
17: "seventeen",
18: "eighteen",
19: "nineteen",
20: "twenty",
30: "thirty",
40: "forty",
50: "fifty",
60: "sixty",
70: "seventy",
80: "eighty",
90: "ninety",
};

// Define the convertNumberToWords function
function convertNumberToWords(number) {
// if number present in object no need to go further
if (number in numbersToWords) return numbersToWords[number];

// Initialize the words variable to an empty string
let words = "";

// If the number is greater than or equal to 100, handle the hundreds place (ie, get the number of hundres)
if (number >= 100) {
// Add the word form of the number of hundreds to the words string
words += convertNumberToWords(Math.floor(number / 100)) + " hundred";

// Remove the hundreds place from the number
number %= 100;
}

// If the number is greater than zero, handle the remaining digits
if (number > 0) {
// If the words string is not empty, add "and"
if (words !== "") words += " and ";

// If the number is less than 20, look up the word form in the numbersToWords object
if (number < 20) words += numbersToWords[number];
else {
// Otherwise, add the word form of the tens place to the words string
//if number = 37, Math.floor(number /10) will give you 3 and 3 * 10 will give you 30
words += numbersToWords[Math.floor(number / 10) * 10];

// If the ones place is not zero, add the word form of the ones place
if (number % 10 > 0) {
words += "-" + numbersToWords[number % 10];
}
}
}

// Return the word form of the number
return words;
}

console.log(convertNumberToWords(123));

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