[Javascript] convert-object-array-to-hash-map-indexed-by-an-attribute-value-of-the-object

var arr = [
    { key: 'foo', val: 'bar' },
    { key: 'hello', val: 'world' }
];

var result = arr.reduce(function(map, obj) {
    map[obj.key] = obj.val;
    return map;
}, {});

console.log(result);
// { foo: 'bar', hello: 'world' }

Note: Array.prototype.reduce() is IE9+, so if you need to support older browsers you will need to polyfill it.

from http://stackoverflow.com/questions/26264956/convert-object-array-to-hash-map-indexed-by-an-attribute-value-of-the-object

from https://lodash.com/docs#indexBy

var keyData = [
  { 'dir': 'left', 'code': 97 },
  { 'dir': 'right', 'code': 100 }
];

_.indexBy(keyData, 'dir');
// → { 'left': { 'dir': 'left', 'code': 97 }, 'right': { 'dir': 'right', 'code': 100 } }

_.indexBy(keyData, function(object) {
  return String.fromCharCode(object.code);
});
// → { 'a': { 'dir': 'left', 'code': 97 }, 'd': { 'dir': 'right', 'code': 100 } }

_.indexBy(keyData, function(object) {
  return this.fromCharCode(object.code);
}, String);
// → { 'a': { 'dir': 'left', 'code': 97 }, 'd': { 'dir': 'right', 'code': 100 } }