Match words not beginning with &

Question

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
Foobar
Bar Foo
BarFoo
Bar Foobar
$Foobar
$Foo$
Foo $Foo %Foo &Foo Foo

Avinash Raj Avinash Raj · Accepted Answer · 2014-11-24T11:18:40

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'

Match words not beginning with &

2 Answers