JavaScript regex - How to wrap matches with tag?

Question

I have a string in JavaScript in which I\'d like to find all matches of a given phrase and wrap them with a tag. I haven\'t been able to find the right regex method here to

Answer 1

You can solve it very simple, just use a capturing group with the word you want, and then use the replacement string <em>$1</em>. You can use a regex like this:

(cat)

working demo

Below, you can see in green the matches (capturing the word cat insensitively) and in the substitution section you can see the replacements.

You can use this code:

var re = /(cat)/ig; 
var str = '"I like to play with cats, as does Cathy, who is a member of ACATA, which is the American Cat And Tiger Association."\n';
var subst = '<em>$1</em>'; 

var result = str.replace(re, subst);

Answer 2

You could use:

"Foo bar cat".replace(/(cat)/ig, "<em>$1</em>");

Which will return:

"Foo bar <em>cat</em>"

Answer 3

One needs no capturing group around the whole regex because there is a $& placeholder that refers to the whole match from the string replacement pattern:

"Foo bar cat".replace(/cat/ig, "<em>$&</em>");
                                    ^^

See the Specifying a string as a parameter section:

$&    Inserts the matched substring.

Thus, no need of any callback methods or redundant regex constructs.

Answer 4

You can do straight-up replace by using a replace function:

str.replace(/cat/ig, function replace(match) { 
    return '<em>' + match + '</em>'; 
});