qasje

'use strict';

// Plunker may spam in console
console.clear();

// Input string
var string = 'The quick brown fox jumped over the lazy dog.';

// Replacements
var matches = {
  'quick': 'slow',
  'brown': 'black',
  'fox': 'bear'
};

// Gogo
var result = string.replace(
  // Match all keys
  new RegExp(Object.keys(matches).join('|'), 'g'),
  // Just get value  from replacements 
  function(match) {
    return matches[match];
  }
);

// Bingo
console.log(result);