Html regex pattern: [\d\s-]{3} works but [\d-\s]{3} doesn't. Why?

Question

Codepen example:
https://codepen.io/Trost/pen/KXBRbY
Try putting 1 symbol in both fields.
I can\'t get what\'s wrong. If I test these regex in https://regex101.com,

Answer 1

You define two different things:

• [a-z] is a definition of a range - all characters from a to z.
• [az-] is a definition of a set of three elements - a, z and -.