CODEWITHSUNDEEP
javascriptregex
signus
signus

Reputation: 1148

Discard 4-digit Number Beginning with Hypen

In attempting some number validation, there is one case I want to exclude a number - if it contains a hyphen before the four digits.

To simplify my regular expression, let's only worry about those 4 digits.

Since I'm using JavaScript, I can't use lookbehinds.

In an attempt to use a negative lookahead to match anything not containing a hyphen, I came up with: 

((?!-).)\d{4}

My test data is below, bolded are the matches:

2014
1106 **2014** **9899**
**11500**

234-233-2014
234-234-1100
-1100

Where my expectation is that 2014, 1106, 2014 and 9989 match, whereas 11500 does not. I know the issue is with the period is due to the fact that it matches anything except for line breaks. I also am trying to consider line breaks as I apply the word boundaries to my regular expression.

Might there be a better solution where I can match only a 4 digit number not followed by a hyphen, or simply exclude any matches if they are preceded by a hyphen?

Upvotes: 0

Views: 105

Answers (4)

Avinash Raj
Avinash Raj

Reputation: 174806

Through regex only,

(?:(?!\b-\b|-\b)(?:.|^))\b(\d{4})\b

Get the numbers from group index 1.

DEMO

And your js code would be,

> console.log(text.match(/(?:(?!\b-\b|-\b)(?:.|^))\b(\d{4})\b/g));
[ '2014', ' 1106', ' 2014', ' 9899' ]

OR

> function getMatches(string, regex, index) {
... index || (index = 1);
... var matches = [];
... var match;
...     while (match = regex.exec(string)) {
.....         matches.push(match[index]);
.....     }
... console.log(matches);
... }
undefined
> var matches = getMatches(text, re, 1);
[ '2014', '1106', '2014', '9899' ]

Code stolen from here :-)

Upvotes: 2

hex494D49
hex494D49

Reputation: 9245

This is a workaround in JavaScript using replace()

var text = "2014 \
1106 2014 9899 \
 11500 \
\
234-233-2014 \
234-234-1100 \
-1100";

var a = [];
text.replace(/(-?\b\d{4}\b)/g, function(m){
  if(!m.match(/-/g)) a.push(m);  
});

console.log(a);

Output:

["2014", "1106", "2014", "9899"]

Working jsBin

Previous attempt (using look-behind which isn't supported in JavaScript)

/(?<!-)\b(\d{4})\b/g

Demo

Upvotes: 0

sahbeewah
sahbeewah

Reputation: 2690

Match either four digits that are the beginning of a line, or four digits that don't come after a hyphen:

/[^-]\b\d{4}\b|^\b\d{4}\b/

Upvotes: 0

OnlineCop
OnlineCop

Reputation: 4069

Although this doubles up your searches, you can do a lookahead with both a positive and negative component to it:

(?=(?!-)\d{4})\b\d{4,}\b

This regex101 example doesn't capture the numbers, where this regex101 example does.

Upvotes: 1

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