Replacing digits to form binary using JavaScript

We need to write a JavaScript function that converts a string of digits into a binary-like representation by replacing digits below 5 with '0' and digits 5 and above with '1'.

Problem Statement

Given a string containing digits, transform it using these rules:

• Digits 0, 1, 2, 3, 4 ? '0'
• Digits 5, 6, 7, 8, 9 ? '1'

Using For Loop

const str = '262355677834342';

const convert = (str = '') => {
    let res = '';
    for(let i = 0; i < str.length; i++){
        const el = +str[i];
        if(el < 5){
            res += 0;
        } else {
            res += 1;
        }
    }
    return res;
};

console.log(convert(str));

010011111100000

Using Array Methods

const str = '262355677834342';

const convertWithMap = (str = '') => {
    return str.split('').map(digit => +digit < 5 ? '0' : '1').join('');
};

console.log(convertWithMap(str));

010011111100000

Using Regular Expression

const str = '262355677834342';

const convertWithRegex = (str = '') => {
    return str.replace(/[0-4]/g, '0').replace(/[5-9]/g, '1');
};

console.log(convertWithRegex(str));

010011111100000

Comparison

Conclusion

All three methods effectively convert digits to binary representation. The array method offers the best balance of readability and conciseness, while the for loop provides optimal performance for large strings.