Find color in the format #abc or #abcdef

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Write a RegExp that matches colors in the format #abc or #abcdef. That is: # followed by 3 or 6 hexadecimal digits.

Usage example:

          let regexp = /your regexp/g;

let str = "color: #3f3; background-color: #AA00ef; and: #abcd";

alert( str.match(regexp) ); // #3f3 #AA00ef

P.S. This should be exactly 3 or 6 hex digits. Values with 4 digits, such as #abcd, should not match.

A regexp to search 3-digit color #abc: /#[a-f0-9]{3}/i.

We can add exactly 3 more optional hex digits. We don’t need more or less. The color has either 3 or 6 digits.

Let’s use the quantifier {1,2} for that: we’ll have /#([a-f0-9]{3}){1,2}/i.

Here the pattern [a-f0-9]{3} is enclosed in parentheses to apply the quantifier {1,2}.

In action:

let regexp = /#([a-f0-9]{3}){1,2}/gi;

let str = "color: #3f3; background-color: #AA00ef; and: #abcd";

alert( str.match(regexp) ); // #3f3 #AA00ef #abc

There’s a minor problem here: the pattern found #abc in #abcd. To prevent that we can add \b to the end:

let regexp = /#([a-f0-9]{3}){1,2}\b/gi;

let str = "color: #3f3; background-color: #AA00ef; and: #abcd";

alert( str.match(regexp) ); // #3f3 #AA00ef