javascript implementation of java's string.hashcode() method

hashcode.js

// 2 April 2019
// hashcode algo
// from http://werxltd.com/wp/2010/05/13/javascript-implementation-of-javas-string-hashcode-method/
// stolen from jjdubray
// see https://medium.com/@metapgmr/hex-a-no-framework-approach-to-building-modern-web-apps-e43f74190b9c

function hashCode(s) {
  var h = 0
  
  return !s || !s.length
    ? h
    : String(s).split('').reduce(function(h, c) {
      return ((h << 5) - h) + c.charCodeAt(0) << 0
    }, h);
}

var tests = [
  null, undefined, , '', false, 0, NaN,
  true,
  'hello', 
  {
    h: 'h', e: 'e', l: 'l', o: 'o'
  },
  [
    'hello'
  ],
  [
    'h','e', 'l', 'l', 'o'
  ]
];

var results = tests.map(function(test) {
  return { input: test, result: hashCode(test) };
})

console.log(
  JSON.stringify(results, null, 2)
);

/*
[
  {
    "input": null,
    "result": 0
  },
  {
    "result": 0
  },
  null,
  {
    "input": "",
    "result": 0
  },
  {
    "input": false,
    "result": 0
  },
  {
    "input": 0,
    "result": 0
  },
  {
    "input": null,
    "result": 0
  },
  {
    "input": true,
    "result": 0
  },
  {
    "input": "hello",
    "result": 99162322
  },
  {
    "input": {
      "h": "h",
      "e": "e",
      "l": "l",
      "o": "o"
    },
    "result": 0
  },
  {
    "input": [
      "hello"
    ],
    "result": 99162322
  },
  {
    "input": [
      "h",
      "e",
      "l",
      "l",
      "o"
    ],
    "result": 1181937828
  }
]
*/