convert array of words (strings) to regex and use it to get matches on a string

Question

What is the most concise and efficient way to translate an array of strings in a regex and then use the regex multiple times on different strings to get the result matches a

Answer 1

Just join with pipeline, using Array.join

var regexFromMyArray = new RegExp(myArray.join("|"), 'gi');

and just do this as if condition is just redundant.

for(var i = 0; i < matches.length; i++)
   console.log("Found:", matches[i]);

1. A single method is being used instead of initial 3. (toString internally calls join(",")) and replace function is also not used.
2. We have removed an unnecessary if-condition. So that's pretty quick.

And since you talk about regexes, I'd like to say that

1. A single regex initialization isn't going to cost you much.
2. If your objective is really to match the words in the array, then just go with String.indexOf, which is a non-regex form of solving the same.