`substr()` is in Core JavaScript 1.2 (pre-ECMA standard), [del]introduced with Netscape Navigator 3.0, which was officially launched in Dec. 1996.[/del]

Edit/correction: Core JS 1.2 was Netscape Communicator 4.0, which was in beta in 1996 and launched in June 1997! (The 4.0x series was still pre-ECMA, as opposed to the 4.x series.)

Yeah that one caught me off guard too. Any idea why? The only reason I can think of is that it's very easy to confuse with `substring`.