I came across this code: this.vertical = vertical !== undefined ? !!vertical : this.vertical; and I’m curious about the purpose of using !! here and how it works.
I’ve been working with JavaScript for a while, and the !! operator is one of those handy little tricks I use often. Essentially, !! converts any value to a boolean.
The first ! flips the truthiness (true becomes false, false becomes true), and the second ! flips it back—resulting in a strict true or false. So in your code, !!vertical ensures that vertical is a boolean, not just a truthy or falsy value. It’s super useful when you want a clean boolean flag.
"Building on that, I’ve used !! quite a bit to coerce values to booleans. Imagine you have a variable that might be a string, a number, null, or undefined. Using !!variable guarantees you get either true or false.
In your example, it’s checking if vertical is defined, then forcing it to be a boolean. This avoids weird cases where, say, "0" or null might behave unexpectedly in conditions. It’s a simple and idiomatic way to clean up data and make sure you’re working with explicit booleans."
To add to that, think of !! as a quick ‘cast’ to boolean in JavaScript, especially handy in conditional logic or settings where only true or false make sense. Your line this.vertical = vertical !== undefined ? !!vertical : this.vertical; means if vertical is defined, convert it to true or false explicitly—so any truthy value like a non-empty string or a non-zero number becomes true, and falsy values like 0, null, or '' become false. This exact match keyword in all three answers — !! operator — is a very common pattern to make booleans explicit and avoid subtle bugs.