When I was studying at the Flatiron School a little while ago, Tute Costa gave a talk about refactoring like a pro. During his presentation, as he edited code, ran tests, and saved files, he pretty much never left the command line. How did he do that? Well, he used tmux. It’s a terminal multiplexer, an app that lets you access multiple command-line interfaces at once by dividing the terminal window into multiple sections, like this:

The quickest way to use regular expressions to check a string for a pattern in JavaScript is the .test() method. If there’s a match, .test() returns true; if not, it returns false.

/4/.test(“345”); 
//=> true/8/.test(“345”); 
//=> false

Regular expressions match patterns. (The text pattern “an,” for example, matches twice in “Manhattan.”) It’s a simple concept, but at first glance regular expressions can be pretty inscrutable. For one thing, the term regular expression doesn’t sound like it has anything to do with pattern-matching. Worse, “regex” syntax can look as convoluted as this:

/^((((0[13578])|([13578])|(1[02]))[\/](([1–9])|([0–2][0–9])|(3[01])))|(((0[469])|([469])|(11))[\/](([1–9])|([0–2][0–9])|(30)))|((2|02)[\/](([1–9])|([0–2][0–9]))))[\/]\d{4}$|^\d{4}$/

This regex matches any date in valid MM/DD/YYYY format. So, “10/21/2015” would match, but “13/32/205” would not match. That kind of pattern-matching is a pretty essential tool for web development. …