multi match and replace regex.js

// From: http://jsfiddle.net/L6LB2/1/
var str = "AddMediaItemTrack";
var words = ["Add", "Track", "Ma"]

var mapObj = {}
for( word of words ) {
  mapObj[word] = "<mark>" + word + "</mark>"
}


var re = new RegExp(Object.keys(mapObj).join("|"),"gi");
str = str.replace(re, function(matched){
  return mapObj[matched];
});

console.log(str);