CODEWITHSUNDEEP
javascriptregex
Ismail Sahin
Ismail Sahin

Reputation: 2710

javascript regex find words containing only one dot

I have program:

var str = "ac.def=1 and xy.z.kt='10' and k.t=1 or xy.z.kt.lm='10'";
var regex = new RegExp('^[a-zA-Z0-9,]*[.]{1}[^=]');
var result = str.split(" ").filter((elem, index) => {
    return regex.test(elem);
})

console.log(result);

I get result as: ["ac.def=1", "xy.z.kt='10'", "k.t=1", "xy.z.kt.lm='10'"]

but I need to get only : ["abc.def=1", "k.t=1"]

it is said that my question is possible duplicate of Learning Regular Expressions so lets close stackoverflow forever, because all questions about software programming has an answer in their own official documents.

Please be careful when marking a question as a possible duplicate of an official documents. Otherwise we should close all questions about regex since Learning Regular Expressions is enough to solve all problems about regex. Right?

Upvotes: 1

Views: 867

Answers (1)

Wiktor Stribiżew
Wiktor Stribiżew

Reputation: 627607

You may use the /^[^.]*\.[^.]*$/ regex:

var str = "ac.def=1 and xy.z.kt='10' and k.t=1 or xy.z.kt.lm='10'";
var regex = /^[^.]*\.[^.]*$/;
var result = str.split(" ").filter((elem, index) => {
    return regex.test(elem);
})

console.log(result);

Pattern details

  • ^ - start of string
  • [^.]* - 0+ chars other than .
  • \. - a dot
  • [^.]* - 0+ chars
  • $ - end of string.

See the regex demo.

Alternative, single-regex, solution

You may collect your matches using a single regex like

/(?:^|\s)([^.\s]*\.[^.\s]*)(?!\S)/g

See the regex demo.

Details

  • (?:^|\s) - a non-capturing group matching start of string or whitespace
  • ([^.\s]*\.[^.\s]*) - Capturing group 1:
    • [^.\s]* - 0+ chars other than a . and whitespace
    • \. - a dot
    • [^.\s]* - 0+ chars other than a . and whitespace
  • (?!\S) - no non-whitespace allowed immediately to the right of the current location (a whitespace or end of string can appear to the right)

JS demo:

var s = "ac.def=1 and xy.z.kt='10' and k.t=1 or xy.z.kt.lm='10'";
var results = [];
s.replace(/(?:^|\s)([^.\s]*\.[^.\s]*)(?!\S)/g, ($0, $1) => results.push($1));
console.log(results);

If there must be a single dot before =, use

/^[^.=]*\.[^.=]*=/

within your code. See the regex demo. The difference is that the regex no longer has $ at the end, = is at the end as it is enough to stop checking there, and = chars are added to the negated character classes to prevent them from matching across these symbols.

Upvotes: 3

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