What are the JavaScript and PHP regex patterns if a string is to fulfill the following conditions:

1. The string should be between (and including) 4 and 20 characters
2. It can contain only lowercase alphabets and, optionally, digits.
3. It MUST contain at least 1 alphabet

The following strings formats are acceptable :

• randy
• randy39
• 39randy
• r789456123

The following are NOT acceptable:

• ran
• 3546
• r_andy
• __3912

What are the JavaScript and PHP regex patterns if a string is to fulfill the following conditions:

1. The string should be between (and including) 4 and 20 characters
2. It can contain only lowercase alphabets and, optionally, digits.
3. It MUST contain at least 1 alphabet

The following strings formats are acceptable :

• randy
• randy39
• 39randy
• r789456123

The following are NOT acceptable:

• ran
• 3546
• r_andy
• __3912

• php
• javascript
• regex

Share Improve this question Follow edited Sep 10, 2012 at 20:58 Wiseguy 20.9k99 gold badges6767 silver badges8383 bronze badges asked Jan 3, 2012 at 11:22 dinchakpianistdinchakpianist 21911 gold badge44 silver badges1212 bronze badges 3

• 5 Have you tried something to solve your task or you just came to SO for munity to do your work? – zerkms Commented Jan 3, 2012 at 11:23
• I've tried /^([a-z0-9]){3,5}$/ – dinchakpianist Commented Jan 3, 2012 at 11:25
• Try /^([a-z0-9]{4,20})$/ if you need the capturing brackets, or /^[a-z0-9]{4,20}$/ if you don't, but that doesn't test for at least 1 alpha – Mark Baker Commented Jan 3, 2012 at 11:30

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2 Answers 2

Sorted by: Reset to default 6

You could use a lookahead assertion to verify that the string contains a letter somewhere.

/^(?=.*[a-z])[a-z0-9]{4,20}$/

This should work in both JavaScript and PHP alike.

Use two regexes: /^[a-z0-9]{4,20}$/ and /[a-z]/ (the actual syntax might differ between PHP and Javascript)