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How to remove invalid UTF-8 characters from a JavaScript string?

rated 0 times [ 124] [ 2] / answers: 1 / hits: 83690 / 14 Years ago, mon, april 19, 2010, 12:00:00

I'd like to remove all invalid UTF-8 characters from a string in JavaScript. I've tried with this JavaScript:

strTest = strTest.replace(/([x00-x7F]|[xC0-xDF][x80-xBF]|[xE0-xEF][x80-xBF]{2}|[xF0-xF7][x80-xBF]{3})|./g, $1);

It seems that the UTF-8 validation regex described here (link removed) is more complete and I adapted it in the same way like:

strTest = strTest.replace(/([x09x0Ax0Dx20-x7E]|[xC2-xDF][x80-xBF]|xE0[xA0-xBF][x80-xBF]|[xE1-xECxEExEF][x80-xBF]{2}|xED[x80-x9F][x80-xBF]|xF0[x90-xBF][x80-xBF]{2}|[xF1-xF3][x80-xBF]{3}|xF4[x80-x8F][x80-xBF]{2})|./g, $1);

Both of these pieces of code seem to be allowing valid UTF-8 through, but aren't filtering out hardly any of the bad UTF-8 characters from my test data: UTF-8 decoder capability and stress test. Either the bad characters come through unchanged or seem to have some of their bytes removed creating a new, invalid character.

I'm not very familiar with the UTF-8 standard or with multibyte in JavaScript so I'm not sure if I'm failing to represent proper UTF-8 in the regex or if I'm applying that regex improperly in JavaScript.

Edit: added global flag to my regex per Tomalak's comment - however this still isn't working for me. I'm abandoning doing this on the client side per bobince's comment.

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3 Years ago

answered 14 Years ago dominickmackenziet · Accepted Answer

I use this simple and sturdy approach:

function cleanString(input) {

    var output = ;

    for (var i=0; i<input.length; i++) {

        if (input.charCodeAt(i) <= 127) {

            output += input.charAt(i);

        }

    }

    return output;

}

Basically all you really want are the ASCII chars 0-127 so just rebuild the string char by char. If it's a good char, keep it - if not, ditch it. Pretty robust and if if sanitation is your goal, it's fast enough (in fact it's really fast).