locales Optional

A string with a BCP 47 language tag or an Intl.Locale instance, or an array of such locale identifiers. For the general form and interpretation of the locales argument, see the parameter description on the Intl main page.

The following Unicode extension keys are allowed:

co

See collation.

kn

See numeric.

kf

See caseFirst.

These keys can also be set with options (as listed below). When both are set, the options property takes precedence.

options Optional

An object containing the following properties, in the order they are retrieved (all of them are optional):

usage

Whether the comparison is for sorting a list of strings or fuzzy (for the Latin script diacritic-insensitive and case-insensitive) filtering a list of strings by key. Possible values are:

"sort" (default)

For sorting a list of strings.

"search"

For filtering a list of strings by testing each list item for a full-string match against a key. With "search", the caller should only pay attention to whether compare() returns zero or non-zero and should not distinguish the non-zero return values from each other. That is, it is inappropriate to use "search" for sorting/ordering.

localeMatcher

The locale matching algorithm to use. Possible values are "lookup" and "best fit"; the default is "best fit". For information about this option, see Locale identification and negotiation.

collation

Variant collations for certain locales, such as "emoji", "pinyin", "stroke", and so on. For a list of supported collation types, see Intl.Locale.prototype.getCollations(); the default is "default". This option can also be set through the co Unicode extension key; if both are provided, this options property takes precedence.

numeric

Whether numeric collation should be used, such that "1" < "2" < "10". Possible values are true and false; the default is false. This option can also be set through the kn Unicode extension key; if both are provided, this options property takes precedence.

caseFirst

Whether upper case or lower case should sort first. Possible values are "upper", "lower", and "false" (use the locale's default); the default is "false". This option can also be set through the kf Unicode extension key; if both are provided, this options property takes precedence.

sensitivity

Which differences in the strings should lead to non-zero result values. Possible values are:

"base"

Only strings that differ in base letters compare as unequal. Examples: a ≠ b, a = á, a = A.

"accent"

Only strings that differ in base letters or accents and other diacritic marks compare as unequal. Examples: a ≠ b, a ≠ á, a = A.

"case"

Only strings that differ in base letters or case compare as unequal. Examples: a ≠ b, a = á, a ≠ A.

"variant"

Strings that differ in base letters, accents and other diacritic marks, or case compare as unequal. Other differences may also be taken into consideration. Examples: a ≠ b, a ≠ á, a ≠ A.

The default is "variant" for usage "sort"; it's locale dependent for usage "search" per spec, but the core functionality of "search" is accent-insensitive and case-insensitive filtering, so "base" makes the most sense (and perhaps "case").

ignorePunctuation

Whether punctuation should be ignored. Possible values are true and false; the default is false.

RangeError

Thrown if locales or options contain invalid values.

The following example demonstrates the different potential results for a string occurring before, after, or at the same level as another:

console.log(new Intl.Collator().compare("a", "c")); // -1, or some other negative value
console.log(new Intl.Collator().compare("c", "a")); // 1, or some other positive value
console.log(new Intl.Collator().compare("a", "a")); // 0

Note that the results shown in the code above can vary between browsers and browser versions. This is because the values are implementation-specific. That is, the specification requires only that the before and after values are negative and positive.

When usage is "search", the caller should only pay attention to whether the return value of compare() is zero or non-zero. It is inappropriate to use a Collator with usage "search" for sorting.

• Intl.Collator
• Intl