.localeCompare()

In JavaScript, the .localeCompare() method returns a number indicating whether the reference string comes before, after, or is the same as the given string in locale-aware lexicographic order. It can take a locales argument to follow the sorting rules of specific languages.

Syntax

string.localeCompare(compareString, locales, options)

Parameters:

• compareString: The string to compare with the reference string (the one .localeCompare() is called on).
• locales (optional): A string containing a BCP 47 language tag (e.g., "en", "de", "fr"), or an array of such strings, specifying the locale(s) to use.
• options (optional): An object that customizes the comparison behavior. The accepted properties are defined by the Intl.Collator constructor (e.g., sensitivity, numeric, ignorePunctuation, etc.).

Return value:

Returns a number indicating the sort order between the reference string and the compareString:

• -1 if the reference string comes before compareString
• 0 if the strings are equal
• 1 if the reference string comes after compareString

Note: The exact result of .localeCompare() can vary depending on the specified locales and options. While the return value is always negative, zero, or positive, the exact numeric value (e.g., -1, 1) may vary across browsers and environments. Therefore, it’s best to check the sign of the result rather than its exact value.

Example

This example shows how to use .localeCompare() to get the alphabetical order of a string compared to a reference string:

const comparison1 = 'boat'.localeCompare('car');
const comparison2 = 'boat'.localeCompare('airplane');
const comparison3 = 'boat'.localeCompare('BOAT', 'en', { sensitivity: 'base' }); // option argument to make the comparison case insensitive

console.log(`"boat" compared with "car": ${comparison1}`);
console.log(`"boat" compared with "airplane": ${comparison2}`);
console.log(`"boat" compared with "BOAT": ${comparison3}`);

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The output of this code is:

"boat" compared with "car": -1
"boat" compared with "airplane": 1
"boat" compared with "BOAT": 0

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Codebyte Example

Run the following codebyte to understand how .localeCompare() works with different locales:

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