misc-utils-of-mine-generic/src/string/hash.ts

Miscellaneous utilities for JavaScript/TypeScript that I often use

/**
 * Returns a hash code for a string.
 * (Compatible to Java's String.hashCode())
 *
 * The hash code for a string object is computed as
 *     `s[0]*31^(n-1) + s[1]*31^(n-2) + ... + s[n-1]`
 * using number arithmetic, where s[i] is the i th character
 * of the given string, n is the length of the string,
 * and ^ indicates exponentiation.
 * (The hash value of the empty string is zero.)
 *
 * @param {string} s a string
 * @return {number} a hash code value for the given string.
 */
export function hashCode(s: string) {
  var h = 0, l = s.length, i = 0
  if (l > 0) {
    while (i < l) {
      h = (h << 5) - h + s.charCodeAt(i++) | 0
    }
  }
  return h
}