String Concatenation vs. Array.join

This cannot be stressed enough, doing many string concatenation operations can be a major hit on performance, and it's easy to avoid in many situations. Consider for example that you want to build a string out of many pieces, one bad way to do this is using the + to concatenate all pieces into a huge string, one piece at a time:



This method will result in too many intermediate strings and concatenation operations, and will poorly perform overall.

A better approach to this problem is using Array.join(), this method joins all array elements into one string:



This method doesn't suffer from the extra string objects, and generally executes faster.