I'm created this regex to match telephone numbers that have three specific prefixes, but it's not perfect. I need a regex that will only match numbers with the prefixes 48, 420, 421 and nothing else.

^[ ][4](8|2)[0-9]{1,14}\d

When the Input is 421 456 456 456ioejkfoi312 I want the regular expression to match 421 456 456 456.

CodePudding user response：

I think this works perfectly.

console.log(/\ 420\s*\d{1,5}\s*\d{1,5}\s*\d{1,5}|\ 421\s*\d{1,5}\s*\d{1,5}\s*\d{1,5}|48\s*\d{1,5}\s*\d{1,5}\s*\d{1,5}/.test(" 48123")) // true
console.log(/\ 420\s*\d{1,5}\s*\d{1,5}\s*\d{1,5}|\ 421\s*\d{1,5}\s*\d{1,5}\s*\d{1,5}|48\s*\d{1,5}\s*\d{1,5}\s*\d{1,5}/.test(" 420 123")) // true
console.log(/\ 420\s*\d{1,5}\s*\d{1,5}\s*\d{1,5}|\ 421\s*\d{1,5}\s*\d{1,5}\s*\d{1,5}|48\s*\d{1,5}\s*\d{1,5}\s*\d{1,5}/.test(" 421 12 3")) // true
console.log(/\ 420\s*\d{1,5}\s*\d{1,5}\s*\d{1,5}|\ 421\s*\d{1,5}\s*\d{1,5}\s*\d{1,5}|48\s*\d{1,5}\s*\d{1,5}\s*\d{1,5}/.test(" 422123")) // false
console.log(/\ 420\s*\d{1,5}\s*\d{1,5}\s*\d{1,5}|\ 421\s*\d{1,5}\s*\d{1,5}\s*\d{1,5}|48\s*\d{1,5}\s*\d{1,5}\s*\d{1,5}/.test(" 41123")) // false
console.log(/\ 420\s*\d{1,5}\s*\d{1,5}\s*\d{1,5}|\ 421\s*\d{1,5}\s*\d{1,5}\s*\d{1,5}|48\s*\d{1,5}\s*\d{1,5}\s*\d{1,5}/.test(" 421456456456")) // true

Anything else gives false