Sorting Strings with Accented Characters

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Strings can create a whole host of problems within any programming language.  Whether it's a simple string, a string containing emojis, html entities, and even accented characters, if we don't scrub data or make the right string handling choices, we can be in a world of hurt.

While looking through Joel Lovera's JSTips repo, I spotted a string case that I hadn't run into yet (...I probably have but didn't notice it):  sorting accented characters to get the desired outcome.  The truth is that accented characters are handled a bit differently than you'd think during a sort:

// Spanish
['único','árbol', 'cosas', 'fútbol'].sort();
// ["cosas", "fútbol", "árbol", "único"] // bad order

// German
['Woche', 'wöchentlich', 'wäre', 'Wann'].sort();
// ["Wann", "Woche", "wäre", "wöchentlich"] // bad order

Yikes -- accented characters don't simply follow their unaccented character counterparts.  By taking an extra step, i.e. localeCompare, we can ensure that our strings are sorted in the way we likely wanted in the first place:

['único','árbol', 'cosas', 'fútbol'].sort(function (a, b) {
  return a.localeCompare(b);
});
// ["árbol", "cosas", "fútbol", "único"]

['Woche', 'wöchentlich', 'wäre', 'Wann'].sort(function (a, b) {
  return a.localeCompare(b);
});
// ["Wann", "wäre", "Woche", "wöchentlich"]

// Or even use Intl.Collator!
['único','árbol', 'cosas', 'fútbol'].sort(Intl.Collator().compare);
// ["árbol", "cosas", "fútbol", "único"]

['Woche', 'wöchentlich', 'wäre', 'Wann'].sort(Intl.Collator().compare);
// ["Wann", "wäre", "Woche", "wöchentlich"]

Localization is already a big challenge without the added confusion that comes with accented characters.  Keep localeCompare and Intl.Collator in mind every time you want to sort strings!

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Discussion

  1. only problem is that this approach is slower, there is a solution which is to use a Intl.Collator object which speeds things up

    https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/localeCompare

    It has other benefits too, such as support for numeric sorts, aka natural or human sorting, so that numerics are also sorted as humans expect, i.e 10 comes after 2

    https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Collator

  2. Nifty, except that ["Wann", "wäre", "Woche", "wöchentlich"] is not the correct order when sorting in German. So it’s not really internationalized, it’s just sorting in a way an English speaker would prefer. A native German would be very confused if you sorted thing this way.

    • Of course if localeCompare is run in the browser, and the user has a German language setting, it would be sorted as expected. My point is that it is dangerous to assume that all languages are sorted the same way.

  3. Gustavo Costa

    Is it possible to sort mixed numbers (numerically by first) and accented or non-accented letters (alphabetically by second)?

  4. Gustavo Costa

    Test with this:

    "3", "2", "10", "40", "6", "4", "30", "33", "1", "Gustavo", "julho", "Klaus", "keyboard", "último", "árbol", "uma", "água", "Argentina", "Ángelo", "argelino", "unido"

    .

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