RegEx match exactly 4 digits

Question

Ok, i have a regex pattern like this /^([SW])\\w+([0-9]{4})$/

This pattern should match a string like SW0001 with SW-Prefix an

Answer 1

Let's see what the regex /^([SW])\w+([0-9]{4})$/ match

1. Start with S or W since character class is used
2. One or more alphanumeric character or underscore(\w = [a-zA-Z0-9_])
3. Four digits

This match more than just SW0001.

Use the below regex.

/^SW\d{4}$/

This regex will match string that starts with SW followed by exactly four digits.

Answer 2

in regex,

• ^ means you want to match the start of the string
• $ means you want to match the end of the string

so if you want to match "SW" + exactly 4 digits you need

^SW[0-9]{4}$