Match words not beginning with &

 

I need a regex that can match words (case insensitive) that do not begin with & character

For example search string Foo

Then match would be something like:

  • foo
  • Foo
  • Foo bar
  • Bar Foo
  • Bar Foo
  • Bar Foo bar
  • $ Foo bar
  • $ Foo $
  • Foo $ Foo % Foo &Foo Foo

    • Use a negative lookbehind assertion like below, 

    (?i)(?<!&)foo

    Explanation:

  • (?i) Case insensitive modifier.
  • (?<!&) Negative lookbehind asserts that the match would be preceded by any but not of & character.
  • foo matches the string foo

    • DEMO

    For js, 

    /(?:[^&]|^)(foo)/igm

    Get the string you want from group index 1.

    DEMO 

    > var s = "Foo $Foo %Foo &Foo Foo";
undefined
> var re = /(?:[^&]|^)(foo)/igm;
undefined
> var m;
undefined
> while ((m = re.exec(s)) != null) {
... console.log(m[1]);
... }
Foo
Foo
Foo
Foo

    Through string.replace method. 

    > var s = "Foo $Foo %Foo &Foo Foo";
undefined
> s.replace(/([^&]|^)(foo)/igm, "$1bar")
'bar $bar %bar &Foo bar'

    This should be Javascript-friendly for a pattern. It uses non-capture groups and makes sure that foo is not preceeded by an ampersand (&) 

    (?:[^&])[fF][oO][oO]

    Non-foo characters that are NOT ampersand will show up in the match, but not in the results/capture.

    EDIT: You may use the 'i' flag in your javascript regex syntax to invoke the case-insensitive mode modiefer. Then the pattern would just be (?:[^&])foo

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