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                const _ = {};
/* ==========================================================================
  _.defaults: Add properties to object from sources if object doesn't have them yet,
  then return the object.

  Definition: _.defaults(object, source)


  console.log(_.default({a: 1, b: 2}, {b: 3, c: 4}))
  // => { a: 1, b: 2, c: 4 }

  Instructions: Implement defaults so that you can give default values to the
  weapons object for the weapons you have already disovered are NOT involved
  in the murder

========================================================================== */

_.defaults = function(object, source) {
    // loop through the source
  Object.keys(sources).forEach( source => {
    // check if the property exists on the object
    if (object[source] === undefined) {
      // if it doesn't, add it
      object[source] = sources[source];
      // if it does, skip
  return object;

const discoveredWeapons = {
  Revolver: true
  // add in the weapons you have discovered so far to this object

// Our newest clues!
const newlyDiscoveredWeapons = {
  "Lead Pipe": true,
  Rope: true,
  Wrench: true,
  Revolver: false

const weaponsTracked = _.defaults(discoveredWeapons, newlyDiscoveredWeapons);

// The objects (first argument) should keep their properties.
console.log("1. Objects should keep their properties.", weaponsTracked.Revolver === true);

// The objects (first argument) should get new properties from the source (second argument).
console.log("2. Objects should get new properties from the source.", weaponsTracked.Rope === true);