1//The concise way by using ES6 syntax like this.
2
3const obj = {A : 1, B : 2, C : 3, D : 4}
4 function objectFlip(obj) {
5     return Object.entries(obj).reduce((acc, [key, value]) => (acc[value] = key, acc), {})
6 }
7console.log('input:  ',obj);
8console.log('output: ',objectFlip(obj));
9
10
11
12static objectFlip(obj) {
13  const ret = {};
14  Object.keys(obj).forEach(key => {
15    ret[obj[key]] = key;
16  });
17  return ret;
18}
19//Or using Array.reduce() & Object.keys()
20
21static objectFlip(obj) {
22  return Object.keys(obj).reduce((ret, key) => {
23    ret[obj[key]] = key;
24    return ret;
25  }, {});
26}
27//Or using Array.reduce() & Object.entries()
28
29static objectFlip(obj) {
30  return Object.entries(obj).reduce((ret, entry) => {
31    const [ key, value ] = entry;
32    ret[ value ] = key;
33    return ret;
34  }, {});
35}

1 var object = { 'a': 1, 'b': 2, 'c': 1 };
2//This uses the package lodash
3
4  _.invert(object);
5  // => { '1': 'c', '2': 'b' }
6
7  // with `multiValue`
8  _.invert(object, true);
9  // => { '1': ['a', 'c'], '2': ['b'] }
10
11