Array to Object using Array#reduce

array-to-object.js

var a = [{key: 'a', value: 1}, {key: 'b', value: 2}, {key: 'c', value: 3}];

a.reduce(function(out, item) {
  out[item.key] = item.value;
  return out;
}, {}); // {a: 1, b: 2, c: 3}