To start with - you can get all the data you need through one single call to https://api.twitch.tv/kraken/streams?channel=herpaderpus,turtles_head,.…&callback=?
Then iterate over the received items instead of making a new call for each member.
For each stream that it finds, save that stream as online in some type of variable (a new array, or an object)
Also remember that all of the names need to be lower case in the query string!