reduce.js

//see CONSOLE!
var votes = [
  "angular",
  "angular",
  "react",
  "react",
  "react",
  "angular",
  "ember",
  "react",
  "vanilla"
];

var initialValue = {};

var reducer = function(tally, vote) {
  if (!tally[vote]) {
    tally[vote] = 1;
  } else {
    tally[vote] = tally[vote] + 1;
  }

  return tally;
};

var result = votes.reduce(reducer, initialValue);

console.log(result);