javascript sort array of objects by property

To sort an array of objects by a property, pass a compare function to sort(): users.sort((a, b) => a.age - b.age) for numbers, users.sort((a, b) => a.name.localeCompare(b.name)) for strings. The function returns a negative number when a goes first, a positive one when b goes first, and 0 to keep them in their current order.

Numbers, strings, descending, two keys

cat > sort.mjs <<'EOF'
const users = [
  { name: "Zoe", age: 31, team: "ops" },
  { name: "adam", age: 25, team: "dev" },
  { name: "Émile", age: 31, team: "dev" },
  { name: "Bea", age: 19, team: "ops" },
];
const names = (list) => list.map((u) => u.name).join(", ");

console.log("age asc:  ", names(users.toSorted((a, b) => a.age - b.age)));
console.log("age desc: ", names(users.toSorted((a, b) => b.age - a.age)));
console.log("name <:   ", names(users.toSorted((a, b) => (a.name < b.name ? -1 : a.name > b.name ? 1 : 0))));
console.log("name locale:", names(users.toSorted((a, b) => a.name.localeCompare(b.name, "en"))));
console.log("team, then age:", names(users.toSorted((a, b) => a.team.localeCompare(b.team) || a.age - b.age)));
console.log("original untouched:", names(users));
EOF
node sort.mjs

age asc:   Bea, adam, Zoe, Émile
age desc:  Zoe, Émile, adam, Bea
name <:    Bea, Zoe, adam, Émile
name locale: adam, Bea, Émile, Zoe
team, then age: adam, Émile, Bea, Zoe
original untouched: Zoe, adam, Émile, Bea

The plain < comparison sorts by code unit, so capital letters come before lowercase ones and accented letters go last. localeCompare sorts the way people read. The || trick chains keys: the second comparison only runs when the first returns 0.

Compare functions for common cases

Pitfalls

• In-place mutation. sort() reorders the original array, which can break React state or code that relies on the old order. toSorted() returns a new array (Node.js 20+, current browsers); on older runtimes copy first with [...arr].sort(...).
• Returning a boolean. (a, b) => a.age > b.age returns true/false, which sort reads as 1/0; it never returns a negative number, so results differ between engines. Always return a number.
• Missing properties. If some objects lack the key, a.name.localeCompare throws Cannot read properties of undefined. Default it: (a.name ?? "").localeCompare(b.name ?? "").
• Subtracting strings such as "10" - "9" works only because JavaScript converts them to numbers; non-numeric strings give NaN, which leaves the order undefined.

Confirm it worked

Print the sorted key column, as the example does with map(u => u.name), and check the first and last values. For large arrays, arr.every((x, i) => i === 0 || cmp(arr[i - 1], x) <= 0) returns true when the array is in order.

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