Javascript reduce() on Object

One option would be to reduce the keys():

var o = {     a: {value:1},     b: {value:2},     c: {value:3} };Object.keys(o).reduce(function (previous, key) {    return previous + o[key].value;}, 0);

With this, you'll want to specify an initial value or the 1st round will be 'a' + 2.

If you want the result as an Object ({ value: ... }), you'll have to initialize and return the object each time:

Object.keys(o).reduce(function (previous, key) {    previous.value += o[key].value;    return previous;}, { value: 0 });

What you actually want in this case are the Object.values. Here is a concise ES6 implementation with that in mind:

const add = {  a: {value:1},  b: {value:2},  c: {value:3}}const total = Object.values(add).reduce((t, {value}) => t + value, 0)console.log(total) // 6

or simply:

const add = {  a: 1,  b: 2,  c: 3}const total = Object.values(add).reduce((t, n) => t + n)console.log(total) // 6

ES6 implementation: Object.entries()

const o = {  a: {value: 1},  b: {value: 2},  c: {value: 3}};const total = Object.entries(o).reduce(function (total, pair) {  const [key, value] = pair;  return total + value;}, 0);