relative-time-format-init.js

const rtf = new Intl.RelativeTimeFormat("th", {
    localeMatcher: "best fit",
    numeric: "always",
    style: "long",
});

console.log(rtf.format(-1, "day")); // expected output: 1 วันที่ผ่านมา
console.log(rtf.format(-1, "month")); // expected output: 1 เดือนที่ผ่านมา
console.log(rtf.format(-1, "year")); // expected output: 1 ปีที่แล้ว
console.log(rtf.format(1, "day")); // expected output: ในอีก 1 วัน
console.log(rtf.format(0, "year")); // expected output: ในอีก 0 ปี

const rtf1 = new Intl.RelativeTimeFormat("th", { numeric: "auto" });
console.log(rtf1.format(-1, "day")); // expected output: เมื่อวาน
console.log(rtf1.format(-1, "month")); // expected output: เดือนที่แล้ว
console.log(rtf1.format(-1, "year")); // expected output: ปีที่แล้ว
console.log(rtf1.format(1, "day")); // expected output: พรุ่งนี้
console.log(rtf1.format(0, "year")); // expected output: ปีนี้

const rtf2 = new Intl.RelativeTimeFormat("en", { numeric: "auto" });
console.log(rtf2.format(-1, "day")); // expected output: yesterday
console.log(rtf2.format(-1, "month")); // expected output: last month
console.log(rtf2.format(-1, "year")); // expected output: last year
console.log(rtf2.format(1, "day")); // expected output: tomorrow
console.log(rtf2.format(0, "year")); // expected output: this year