wip(iterator from test): Added jest test to Iterator.from (snapshots failing)

Author: elimanzo

workspaces/adventure-pack/goodies/typescript/Iterator.from/index.test.ts

@@ -0,0 +1,87 @@
+import { describe, expect, it } from "@jest/globals";
+
+import "./index";
+
+describe("Iterator.from", () => {
+  it("can convert an Array to an Iterator", () => {
+    const array = [1, 2, 3];
+    const iterator = Iterator.from(array);
+
+    expect([...iterator]).toStrictEqual(array);
+  });
+
+  it("can convert a Set to an Iterator", () => {
+    const set = new Set([1, 2, 3]);
+    const iterator = Iterator.from(set);
+
+    expect([...iterator]).toStrictEqual([...set]);
+  });
+
+  it("can convert a Map to an Iterator", () => {
+    const map = new Map([
+      ["a", 1],
+      ["b", 2],
+      ["c", 3],
+    ]);
+    const iterator = Iterator.from(map);
+    expect([...iterator]).toStrictEqual([...map.entries()]);
+  });
+
+  it("can convert a Generator Object to an Iterator", () => {
+    const factory = function* (): Generator<number, void, void> {
+      yield 3;
+      yield 1;
+      yield 4;
+      yield 1;
+      yield 5;
+    };
+    const iterator = Iterator.from(factory());
+
+    expect([...iterator]).toStrictEqual([3, 1, 4, 1, 5]);
+  });
+
+  it("can convert a String to an Iterator", () => {
+    const string = "🚀💯🔥";
+    const iterator = Iterator.from(string);
+
+    expect([...iterator]).toStrictEqual([...string]);
+  });
+
+  it("can convert an Iterator to an Iterator", () => {
+    const array = [1, 2, 3];
+    const iterator = Iterator.from(array.values());
+    const iterator2 = Iterator.from(iterator);
+
+    expect([...iterator2]).toStrictEqual(array);
+  });
+
+  it("can convert an IterableIterator to an Iterator", () => {
+    const array = [1, 2, 3];
+    const iterator = Iterator.from(array.values());
+    const iterator2 = Iterator.from(iterator[Symbol.iterator]());
+
+    expect([...iterator2]).toStrictEqual(array);
+  });
+
+  it("can convert an object with a random next() method to an Iterator", () => {
+    const object = {
+      values: [1, 2, 3],
+      index: 0,
+      next() {
+        if (this.index < this.values.length) {
+          return { value: this.values[this.index++], done: false };
+        }
+        return { done: true, value: undefined };
+      },
+    };
+    const iterator = Iterator.from(object);
+
+    expect([...iterator]).toStrictEqual([1, 2, 3]);
+  });
+
+  it("throws an error if the object is not an IterableIterator", () => {
+    const object = {};
+    // @ts-expect-error Invalid argument
+    expect(() => Iterator.from(object)).toThrow(TypeError);
+  });
+});

workspaces/adventure-pack/goodies/typescript/Iterator.from/index.ts

@@ -19,22 +19,25 @@ declare global {
 ).from ??= function <T>(
   object: Iterator<T> | Iterable<T> | { next(): IteratorResult<T> },
 ): IterableIterator<T> {
-  if (Symbol.iterator in object) {
-    return object as IterableIterator<T>;
-  } else if (
-    "toIterable" in object &&
-    typeof (object as Iterator<T>).toIterable === "function"
-  ) {
+  if (typeof (object as Iterable<T>)[Symbol.iterator] === "function") {
+    return (object as Iterable<T>)[Symbol.iterator]() as IterableIterator<T>;
+  }
+
+  if (typeof (object as Iterator<T>).toIterable === "function") {
     return (object as Iterator<T>).toIterable();
-  } else {
+  }
+
+  if (typeof (object as { next(): IteratorResult<T> }).next === "function") {
     return (function* () {
       let result: IteratorResult<T>;
       do {
-        result = object.next();
+        result = (object as { next(): IteratorResult<T> }).next();
         if (!result.done) {
           yield result.value;
         }
       } while (!result.done);
     })();
   }
+
+  throw new TypeError("Object is not an Iterator or Iterable");
 };