Description If elements that are considered equal by sorting then sorting does not change the order of those elements. Example const arr = [ { key: "b", value: 1 }, { key: "a", value: 2 }, { key: "b", value: 3 }, ]; arr.sort((x, y) => x.key.localeCompare(y.key, "en-US")); console.log(arr); // [ { key: 'a', value: 1 }, { key: 'b', value: 1 }, { key: 'b', value: 3 } ]