The collation accessor property of Intl.Locale instances returns the collation type for this locale, which is used to order strings according to the locale's rules.
Description
Collation is the process of ordering strings of characters. It is used whenever strings must be sorted and placed into a certain order, from search query results to ordering records in a database. While the idea of placing strings in order might seem trivial, the idea of order can vary from region to region and language to language. The collation property's value is set at construction time, either through the co key of the locale identifier or through the collation option of the Intl.Locale() constructor. The latter takes priority if they are both present; and if neither is present, the property has value undefined.
For a list of supported collation types, see Intl.Locale.prototype.getCollations().
The set accessor of collation is undefined. You cannot change this property directly.
Examples
Like other locale subtags, the collation type can be added to the Intl.Locale object via the locale string, or a configuration object argument to the constructor.
Adding a collation type via the locale string
In the Unicode locale string spec, collation types are locale key "extension subtags". These subtags add additional data about the locale, and are added to locale identifiers by using the -u extension. Thus, the collation type can be added to the initial locale identifier string that is passed into the Intl.Locale() constructor. To add the collation type, first add the -u extension to the string. Next, add the -co extension to indicate that you are adding a collation type. Finally, add the collation type to the string.
const locale = new Intl.Locale("zh-Hant-u-co-zhuyin");
console.log(locale.collation); // "zhuyin"
Adding a collation type via the configuration object argument
The Intl.Locale() constructor has an optional configuration object argument, which can contain any of several extension types, including collation types. Set the collation property of the configuration object to your desired collation type, and then pass it into the constructor.
const locale = new Intl.Locale("zh-Hant", { collation: "zhuyin" });
console.log(locale.collation); // "zhuyin"