I am trying to create a regular expression in javascript that will match these requirements

• Starts with a 0 but second digit not a 0
• 11-12 characters long
• Must contain exactly 1 space
• No other special characters or letters, just numbers

So far I have come up with ^[0][1-9][\d ]{9,10}$

however, this would still match with 2 spaces or no spaces. I have been so far unsuccessful to find a way to require just one space anywhere within the number. I have tried positive lookahead and found other examples online, however making the quantifier work with the requirement has proven difficult.

I am trying to create a regular expression in javascript that will match these requirements

• Starts with a 0 but second digit not a 0
• 11-12 characters long
• Must contain exactly 1 space
• No other special characters or letters, just numbers

So far I have come up with ^[0][1-9][\d ]{9,10}$

however, this would still match with 2 spaces or no spaces. I have been so far unsuccessful to find a way to require just one space anywhere within the number. I have tried positive lookahead and found other examples online, however making the quantifier work with the requirement has proven difficult.

• javascript
• regex

• Will the non-regex solution work for you? – gurvinder372 Commented May 24, 2016 at 10:41
• It is being used in a HTML5 pattern attribute so needs to be a regex – Lotok Commented May 24, 2016 at 10:42

3 Answers 3

You can use

/^(?=.{11,12}$)(?=\S* \S*$)0[ 1-9][ \d]+$/

See the regex demo

Details:

• ^ - start of string
• (?=.{11,12}$) - total length must be 11 to 12 chars (just a lookahead check, fails the match if the condition is not met)
• (?=\S* \S*$) - there must be 1 space only (just a lookahead check, fails the match if the condition is not met)
• 0 - the first char matched must be 0
• [ 1-9] - the second char is any digit but 0 or space
• [ \d]+ - 1 or more digits or spaces
• $ - end of string.

You can use this regex with positive lookahead:

/^0[1-9](?=\d* \d+$)[ \d]{9,11}$/

RegEx Demo

• (?=\d* \d+$) ensures there is at least a space after first characters
• Using {9,11} as 2 characters have already been matched at start (zero and non-zero)

Here's my attempt. It's slightly faster than Wiktors. And since the time is already spent, I'll share it.

^(?=\d* \d*$)0[1-9 ][\d ]{9,10}$

See it here at regex101.