How to do case insensitive string comparison?

Exploring other case-insensitive comparison methods

Though using the toLowerCase and toUpperCase string methods is straightforward, JavaScript also provides advanced ways to handle complex or more specific scenarios.

Case insensitive string comparison using localeCompare

JavaScript localeCompare allows for locale-sensitive string comparison:

const isItTheSame = "Straße".localeCompare("strasse", undefined, { sensitivity: 'base' }) === 0;
// true in the realm of German language


However, some old browsers may not support localeCompare, so be cautious:

if ("a".localeCompare) {
    // You're good to go
} else {
    // Stick to .toLowerCase() or .toUpperCase()
}


Regular expression for case-insensitive string comparison

If you love flexing your regular-expression muscles, here is a fun way to compare strings insensitively:

const doWeMatch = /^goodbye$/i.test("GOODBYE");
// true, because polite departure knows no case!


Accurate case-insensitive comparison with locale specifics

When dealing with different locales, use toLocaleLowerCase(). It won't mess up your localization efforts:

const isEqualIgnCase = "Istanbul".toLocaleLowerCase('tr-TR') === "istanbul".toLocaleLowerCase('tr-TR');
// true, because, in Turkey, case does not matter!


Handling Unicode and special characters

Comparing strings with Unicode or special characters? Normalizing could help:

// Both will be normalized to canonical form before comparing
"a\u0300".normalize() === "\u00E0".normalize()
// true, unicorns love Unicode normalization!


Compatibility considerations

Beware of feature compatibility. It's always a good idea to check resources like MDN Docs or caniuse.com.

Extra points to consider

JavaScript is like life, it's full of surprises and quirks! Here are some key things to keep an eye on:

Performance implications

Big strings + frequent comparisons = slower performance. JavaScript could have a meltdown if you're not careful! 🌋

Internationalization implications

Keep intl apps in mind: .toUpperCase() / .toLowerCase() might give you migraines with locale issues. 🌍💔

Regex quirks

When using RegExp, special characters can turn the party into a nightmare, so always be on your guard! 💻🦹‍♂️