find if the string contains the characters of substring or not[判断字符串是否包含字符，与顺序无关]

find_character.md

function mutation(arr) {
  //build a regexp
  var regStr = "";
  arr[1].split("").forEach(function(val){
      regStr +="(?=.*?"+val.toLowerCase()+")";
    //just like this "/(?=.*?a)(?=.*?b)(?=.*?c)/"
  });
  var regObj = new RegExp(regStr,"i");
  return regObj.test(arr[0]);
}

mutation(["hello", "hey"]);

refer to this blog