Which came first, JavaScript or Twitter?

JavaScript came first, by 11 years. Brendan Eich wrote it in ten days for Netscape Navigator.

Side by side

JavaScript

JavaScript was written in about ten days in May 1995, shipped in Netscape Navigator 2.0 later that year, and was called LiveScript until December, when Netscape renamed it as part of a marketing deal with Sun. It has nothing to do with Java beyond some borrowed syntax. Standardisation as ECMAScript followed in 1997, and the language spent a decade being treated as a toy before it became the most widely deployed programming language in the world.

Twitter

The first tweet — "just setting up my twttr" — went out on 21 March 2006, and the service opened publicly that July. The 140-character limit came from SMS: a text message allows 160 characters and 20 were reserved for the username. When the limit doubled to 280 in 2017 the SMS constraint had been irrelevant for years.