diff --git a/collections/sort_by.ts b/collections/sort_by.ts
index a9c2d1b474d3..ac70be68e2b7 100644
--- a/collections/sort_by.ts
+++ b/collections/sort_by.ts
@@ -124,16 +124,21 @@ export function sortBy<T>(
     | ((el: T) => Date),
   options?: SortByOptions,
 ): T[] {
-  const array: { value: T; selected: string | number | bigint | Date }[] = [];
+  const array = Array.isArray(iterator) ? iterator : Array.from(iterator);
+  const len = array.length;
+  const selected: (string | number | bigint | Date)[] = new Array(len);
+  const indices: number[] = new Array(len);
 
-  for (const item of iterator) {
-    array.push({ value: item, selected: selector(item) });
+  for (let i = 0; i < len; i++) {
+    selected[i] = selector(array[i]!);
+    indices[i] = i;
   }
 
-  array.sort((oa, ob) => {
-    const a = oa.selected;
-    const b = ob.selected;
-    const order = options?.order === "desc" ? -1 : 1;
+  const order = options?.order === "desc" ? -1 : 1;
+
+  indices.sort((ia, ib) => {
+    const a = selected[ia]!;
+    const b = selected[ib]!;
 
     if (Number.isNaN(a)) return order;
     if (Number.isNaN(b)) return -order;
@@ -141,5 +146,9 @@ export function sortBy<T>(
     return order * (a > b ? 1 : a < b ? -1 : 0);
   });
 
-  return array.map((item) => item.value);
+  const result: T[] = new Array(len);
+  for (let i = 0; i < len; i++) {
+    result[i] = array[indices[i]!]!;
+  }
+  return result;
 }
diff --git a/collections/sort_by_test.ts b/collections/sort_by_test.ts
index 3260fa67caae..4bffec09cd06 100644
--- a/collections/sort_by_test.ts
+++ b/collections/sort_by_test.ts
@@ -34,6 +34,22 @@ Deno.test({
   },
 });
 
+Deno.test({
+  name: "sortBy() handles single element",
+  fn() {
+    const single = [{ value: 42 }];
+    assertEquals(sortBy(single, (it) => it.value), [{ value: 42 }]);
+  },
+});
+
+Deno.test({
+  name: "sortBy() handles two elements",
+  fn() {
+    assertEquals(sortBy([2, 1], (it) => it), [1, 2]);
+    assertEquals(sortBy([1, 2], (it) => it), [1, 2]);
+  },
+});
+
 Deno.test({
   name: "sortBy() handles identity selector",
   fn() {
@@ -146,6 +162,23 @@ Deno.test({
   },
 });
 
+Deno.test({
+  name: "sortBy() handles invalid dates via getTime",
+  fn() {
+    // Use .getTime() to get numeric NaN which triggers proper NaN handling
+    const items = [
+      { id: 1, date: new Date("2020-01-01") },
+      { id: 2, date: new Date("invalid") },
+      { id: 3, date: new Date("2019-01-01") },
+    ];
+    const result = sortBy(items, (it) => it.date.getTime());
+    // NaN from invalid date sorts to end
+    assertEquals(result[0], { id: 3, date: new Date("2019-01-01") });
+    assertEquals(result[1], { id: 1, date: new Date("2020-01-01") });
+    assertEquals(result[2]!.id, 2);
+  },
+});
+
 Deno.test({
   name: "sortBy() handles sortings",
   fn() {
@@ -222,6 +255,16 @@ Deno.test({
   },
 });
 
+Deno.test({
+  name: "sortBy() handles explicit asc ordering",
+  fn() {
+    assertEquals(
+      sortBy([3, 1, 2], (it) => it, { order: "asc" }),
+      [1, 2, 3],
+    );
+  },
+});
+
 Deno.test({
   name: "sortBy() works with iterators",
   fn() {
@@ -254,3 +297,37 @@ Deno.test({
     ]);
   },
 });
+
+Deno.test({
+  name: "sortBy() works with generators",
+  fn() {
+    function* gen() {
+      yield { value: 3 };
+      yield { value: 1 };
+      yield { value: 2 };
+    }
+    assertEquals(sortBy(gen(), (it) => it.value), [
+      { value: 1 },
+      { value: 2 },
+      { value: 3 },
+    ]);
+  },
+});
+
+Deno.test({
+  name: "sortBy() handles large arrays",
+  fn() {
+    const large = Array.from(
+      { length: 10000 },
+      (_, i) => ({ i, rand: Math.random() }),
+    );
+    const sorted = sortBy(large, (it) => it.rand);
+
+    // Verify sorted order
+    for (let i = 1; i < sorted.length; i++) {
+      assertEquals(sorted[i - 1]!.rand <= sorted[i]!.rand, true);
+    }
+    // Verify no elements lost
+    assertEquals(sorted.length, 10000);
+  },
+});