const PRIME_BASE = 257;
const PRIME_MOD = 1000000007;

function polynomialHash(s) {
    let hash = 0;
    for (let i = 0; i < s.length; i++) {
        hash = hash * PRIME_BASE + s.charCodeAt(i);
        hash %= PRIME_MOD; //don't overflow
    }

    return hash;
}

console.log("polynomialHash(Paris)", polynomialHash("Paris"));
console.log("polynomialHash(Auckland)", polynomialHash("Auckland"));
console.log("polynomialHash(Peter)", polynomialHash("Peter"));
console.log("polynomialHash(Dover)", polynomialHash("Dover"));

// Outputs
// polynomialHash(Paris) 651721837
// polynomialHash(Auckland) 56642560
// polynomialHash(Peter) 719751278
// polynomialHash(Dover) 539984858