I was reading this book - Professional Javascript for Web Developers where the author mentions string concatenation is an expensive operation compared to using an array to store strings and then using the join method to create the final string. Curious, I did a couple test here to see how much time it would save and this is what I got -
Somehow, the Firefox usually produces somewhat similar times to both ways, but in IE, string concatenation is much much faster. So, can this idea now be considered outdated (browsers probably have improved since?