JavaScript can run on any device that has a JavaScript Runtime Environment (JRE). The heart of the JRE is the JS Engine — a piece of software (not hardware) that interprets and executes JavaScript.

Sometimes you need to modify your HTML to work around differences in browsers and operating systems. And sometimes you need to do something that HTML just doesn't do ...

Think about the first time you try to scrape a modern flight-booking website. You're looking for ticket prices, and you feel confident. You've found the exact <span ...