Converting number of corresponding string without using library function in JavaScript

Converting a number to a string without using built-in functions like String() or toString() requires extracting individual digits and building the result character by character.

Problem

We need to write a JavaScript function that takes a number and converts it to its corresponding string representation without using the built-in functions String() or toString() or direct string concatenation.

Approach

The solution extracts digits from right to left using the modulo operator (%) and integer division. Each digit is converted to its character representation and prepended to build the final string.

Example

const num = 235456;

const convertToString = (num) => {
    let res = '';
    while(num) {
        res = (num % 10) + res;
        num = Math.floor(num / 10);
    }
    return res;
};

console.log(convertToString(num));
console.log(typeof convertToString(num));

235456
string

How It Works

The algorithm works by:

1. Extract rightmost digit: num % 10 gets the last digit
2. Prepend to result: Add the digit to the front of our result string
3. Remove processed digit: Math.floor(num / 10) removes the last digit
4. Repeat: Continue until no digits remain

Handling Edge Cases

const convertToString = (num) => {
    if (num === 0) return '0';
    
    let res = '';
    let isNegative = num < 0;
    num = Math.abs(num);
    
    while(num) {
        res = (num % 10) + res;
        num = Math.floor(num / 10);
    }
    
    return isNegative ? '-' + res : res;
};

console.log(convertToString(0));      // "0"
console.log(convertToString(-123));   // "-123"
console.log(convertToString(456));    // "456"

0
-123
456

Conclusion

This approach successfully converts numbers to strings by extracting digits mathematically and building the result character by character. The enhanced version handles zero and negative numbers correctly.