string1, string2

The strings to compare against each other.

A number indicating how string1 and string2 compare to each other according to the sort order of this Intl.Collator object:

• A negative value if string1 comes before string2;
• A positive value if string1 comes after string2;
• 0 if they are considered equal.

Use the compare function for sorting arrays. Note that the function is bound to the collator from which it was obtained, so it can be passed directly to Array.prototype.sort().

const a = ["Offenbach", "Österreich", "Odenwald"];
const collator = new Intl.Collator("de-u-co-phonebk");
a.sort(collator.compare);
console.log(a.join(", ")); // "Odenwald, Österreich, Offenbach"

Use the compare function for finding matching strings in arrays:

const a = ["Congrès", "congres", "Assemblée", "poisson"];
const collator = new Intl.Collator("fr", {
  usage: "search",
  sensitivity: "base",
});
const s = "congres";
const matches = a.filter((v) => collator.compare(v, s) === 0);
console.log(matches.join(", ")); // "Congrès, congres"

• Intl.Collator
• String.prototype.localeCompare()