Question

Is it good practice to start all JS files with a semi colon to account for any bad scripts included before it? Or don’t bother?

Thanks

;(function(){ /* my script here */ })();

Answer 1

Do bother, more and more people leverage the power of ASI and write semicolonless JavaScript. In semicolonless JS world that’s the “rule”, you put a semicolon before raw expressions, like ;(), or ;[] or ;//, as well as after 'use strict'; and omit them everywhere else. Raw expressions are not very common, except the typical IIFE.
Even if you write JS with semicolons, that particular one is safe and will do more good than bad.