Google App Script code editor now gives you info on performance

Google have added a new hints feature in the Apps Script code editor: a light bulb. This is icon will be grayed out most of the time, but when it lights up it means that the Google system has some useful information to share about your script, such as performance improvements or warnings about the use of deprecated methods. Google collect this data as your script executes, so you won’t get any hints until after the first time you’ve run it.