Странное сравнение

const readline = require('readline');
const io_interface = readline.createInterface({
    input: process.stdin
});

let lineNumber = 0,
    s,
    t;

io_interface.on('line', function(line) {
    if (lineNumber === 0) {
        s = line;
    } else if (lineNumber < 2) {
        t = line;
    }
    lineNumber++;
})

io_interface.on('close', function() {
    if (isStrangeEqual(s, t)) {
        console.log('YES');
    } else {
        console.log('NO');
    }
})

function isStrangeEqual(s, t) {
        if (s.length !== t.length) {
            return false;
        }
        let map = {};
        for (const index in s) {
            if (!map.hasOwnProperty(s[index].charCodeAt(0))) {
                map[s[index].charCodeAt(0)] = t[index].charCodeAt(0);
            } else {
                if (map[s[index].charCodeAt(0)] !== t[index].charCodeAt(0)) {
                    return false;
                }
            }
        }

        return true;
    }