Third-Party JavaScript

Preface

In February of 2010, I was on the phone with Jason Yan, CTO and cofounder of a web startup called Disqus. At the time, Disqus was a tiny company behind a fast-growing commenting application, distributed as a third-party script and popular with bloggers and a handful of large media companies. Jason was interviewing me for a JavaScript engineering role—their first hire dedicated to working on a fast-growing client codebase.

After a handful of standard JavaScript interview questions involving classes, prototypes, and scopes, Jason took a different tack. He asked me the following (roughly paraphrased) question: “Let’s say I’ve taken a native function prototype—like Array.prototype.indexOf and assigned it a new value. How would you get the ...