Replace string with a function of replaced string

Question

I would like to find a performant and elegant solution to this problem :

I need to replace a substring of a string, case insensitively, by a function of what have been replaced.

Example :

var highlight = function(inputString, filterString) {
    var regex = new RegExp(filterString, 'gi');
    return inputString.replace(regex, '<b>' + filterString + '</b>');
};

highlight('The input', 't');

If your run this in your browser console, you'll get :

"<b>t</b>he inpu<b>t</b>"

My problem is that I'd like to keep the original case of the replaced string. Therefore, the expected result would be :

"<b>T</b>he inpu<b>t</b>"

Any idea ?

Edit: Answer by @georg:

return inputString.replace(regex, '<b>$&</b>');

georg · Accepted Answer · 2015-03-25 09:23:32Z

5

Just use $& in the replacement, which means "what has been found":

var highlight = function(inputString, filterString) {
    var regex = new RegExp(filterString, 'gi');
    return inputString.replace(regex, '<b>$&</b>');
};

x = highlight('The input', 't');
document.write("<pre>" + JSON.stringify(x,0,3));

Other $... magic constructs, for the reference:

enter image description here

MDN

edited Mar 25, 2015 at 9:23

answered Mar 25, 2015 at 9:14

georg

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Comments

Sohan Soni · Accepted Answer · 2015-03-25 09:25:36Z

1

$& contains the string matched by the last pattern match.

Please refer https://msdn.microsoft.com/en-us/library/ie/3k9c4a32%28v=vs.94%29.aspx for more details.

answered Mar 25, 2015 at 9:25

Sohan Soni

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