Javascript string comparison fails when comparing unicode characters

javascript string unicode data-transfer unicode-normalization
tougher picture tougher · May 29, 2012 · Viewed 15.9k times · Source

I want to compare two strings in JavaScript that are the same, and yet the equality operator == returns false. One string contains a special character (eg. the danish å).

JavaScript code:

var filenameFromJS = "Designhåndbog.pdf";
var filenameFromServer = "Designhåndbog.pdf";

print(filenameFromJS == filenameFromServer); // This prints false why?

The solution What worked for me is unicode normalization as slevithan pointed out.

I forked my original jsfiddle to make a version using the normalization lib suggested by slevithan. Link: http://jsfiddle.net/GWZ8j/1/.

Answer

slevithan picture slevithan · May 29, 2012

Unlike what some other people here have said, this has nothing to do with encodings. Rather, your two strings use different code points to render the same visual characters.

To solve this correctly, you need to perform Unicode normalization on the two strings before comparing them. Unforunately, JavaScript doesn't have this functionality built in. Here is a JavaScript library that can perform the normalization for you: https://github.com/walling/unorm

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