How word character is interpreted in character class?

Question

\\w - stands for [A-Za-z0-9_] Character class

But i am not able to understand how it is interpreted inside character class.

So when

Answer 1

I guess range is doing everything here, when you use ^[A-Za-z0-9_-~]+$

_-~ matches a single character in the range between _ (index 95) and ~ (index 126) (case sensitive) that's why T| get matched and returns true but when you use ^[\w-~]+$ it is not forming any range of characters like _-~ to match so it fails and returns false

See ^[A-Za-z0-9-~]+$ also returns false because it doesn't include the _ character to make the range _-~ between _ (index 95) and ~ (index 126)

let test = (str) => /^[A-Za-z0-9-~]+$/.test(str)

console.log(test("T|"))

See https://regex101.com/r/vbLN9L/5 here on the EXPLANATION section.