I interviewed and passed at google. Through 6 interviews I used JS, C, Go, and Swift. One of the tougher Qs was to make a pretty full-featured promise library from scratch in whatever language I wanted in one of those interviews. Chose Swift because I'm a fan of the syntax for blocks (esp when whiteboarding). Feedback was that was my best interview of the day. My experience - they wanted to know I could program, didn't care about language.