I have the following regular expression to validate blood pressure values in the form of systolic/diastolic:

\b[0-9]{1,3}\/[0-9]{1,3}\b

The expression works with the only flaw that it allows more than one non-consecutive slash (/). For example, it allows this 2/2/2. I want it to allow only the format of a number from 1 to 999, and slash, and again a number from 1 to 999. For example, 83/23, 1/123, 999/999, 110/80, etc. Can anybody give me some help with this?

The only other expression I've found is here: ^\b(29[0-9]|2[0-9][0-9]|[01]?[0-9][0-9]?)\\/(29[0-9]|2[0-9][0-9]|[01]?[0-9][0-9]?)$, but it doesn't work.

I have the following regular expression to validate blood pressure values in the form of systolic/diastolic:

\b[0-9]{1,3}\/[0-9]{1,3}\b

The expression works with the only flaw that it allows more than one non-consecutive slash (/). For example, it allows this 2/2/2. I want it to allow only the format of a number from 1 to 999, and slash, and again a number from 1 to 999. For example, 83/23, 1/123, 999/999, 110/80, etc. Can anybody give me some help with this?

The only other expression I've found is here: ^\b(29[0-9]|2[0-9][0-9]|[01]?[0-9][0-9]?)\\/(29[0-9]|2[0-9][0-9]|[01]?[0-9][0-9]?)$, but it doesn't work.

• javascript
• regex

• 2 You should use anchors at both ends. Caret(^) and Dollar($). – Rohit Jain Commented Feb 16, 2013 at 22:18
• How are you using that regex? Can you show some code? – Rohit Jain Commented Feb 16, 2013 at 22:20
• @Rohit: if the blood pressure was the whole of the string, required if it's to match the ^ and $ (unless I'm misunderstanding something, which is possible since I'm still relatively new to RegEx), there'd be no point using RegEx to match it. – David Thomas Commented Feb 16, 2013 at 22:20
• jQuery makes no difference. This is intended for use with Javascript. Also, why Regex at all? Split on / and test for array length and if valid at two, if both are between 1-999. – Jared Farrish Commented Feb 16, 2013 at 22:21
• @RohitJain got it right, you should post an answer.. and the \b boundaries are unecessary when using the carets ^ and $ – kjetilh Commented Feb 16, 2013 at 22:27

4 Answers 4

Use ^ and $ to match the beginning and end of the string:

^\d{1,3}\/\d{1,3}$

By doing so, you force the matched strings to be exactly of that form.

Don't use the \b word-boundaries because a slash counts as a word boundary.

The use of ^ and/or $ is likely your most simple solution. Unfortunately, if your input is a part of a string or sentence or occurs more than once in a line, etc., you've got more thinking to do.

^\b(29[0-9]|2[0-9][0-9]|[01]?[0-9][0-9]?)\/(29[0-9]|2[0-9][0-9]|[01]?[0-9][0-9]?)$

This is correct, the other had one extra \

Expanding on Blender's answer, here is a simple check for validating BP value in the format: 120/80:

if(/^\d{1,3}\/\d{1,3}$/.test(120/80)) {
    console.log("BP Valid");
} else {
    console.log("Invalid BP");
}