仅字母和数字但开头或结尾没有数字的正则表达式

Question

I want to make a regex that matches only letters and numbers, but no numbers at the beginning or the end:

• ahmed0saber is valid
• 0ahmedsaber is not valid
• ahmedsaber0 is not valid
• ahmed_saber is not valid

I tried this

[a-z0-9_]

but it doesn't work as expected!

Answer 1

This should work ^[az][az\d]*[az]$

 const regex = /^[az][az\d]*[az]$/ const tests = ['ahmed0saber', '0ahmedsaber', 'ahmedsaber0', 'ahmed_saber'] tests.forEach(test) function test(name) { console.log(name, name.match(regex)? 'yes': 'no') }

Answer 2

If you also want to allow a single character:

 ^[a-z](?![a-z\d]*\d$)[a-z\d]*$

Explanation

• ^ Start of string
• [az] Match a single char az
• (?![az\d]*\d$) Negative lookahead, assert the the string does not end on a digit
• [az\d]* Match optional chars az or digits
• $ End of string

See a regex demo .

Or if a lookbehind assertion is supported:

^[a-z][a-z\d]*$(?<!\d)

Explanation

• ^ Start of string
• [az] Match a single char az
• [az\d]* Match optional chars az or digits
• $ End of string
• (?<!\d) Negative lookabehind, assert not a digit at the end

See another regex demo .