Merge pull request #8888 from mitar/minimongo-iterator

Make Minimongo cursor iterable.

History.md

@@ -1,5 +1,9 @@
 ## v.NEXT
 
+* Minimongo cursors are now JavaScript iterable objects and can now be iterated over
+  using `for...of` loops, spread operator, `yield*`, and destructuring assignments.
+  [PR #8888](https://github.com/meteor/meteor/pull/8888)
+
 * `meteor list --tree` can now be used to list all transitive package
   dependencies (and versions) in an application. Weakly referenced dependencies
   can also be listed by using the `--weak` option. For more information, run

packages/minimongo/cursor.js

@@ -72,6 +72,35 @@ export default class Cursor {
     return result;
   }
 
+  [Symbol.iterator]() {
+    if (this.reactive) {
+      this._depend({
+        addedBefore: true,
+        removed: true,
+        changed: true,
+        movedBefore: true});
+    }
+
+    let index = 0;
+    const objects = this._getRawObjects({ordered: true});
+
+    return {
+      next: () => {
+        if (index < objects.length) {
+          // This doubles as a clone operation.
+          let element = this._projectionFn(objects[index++]);
+
+          if (this._transform)
+            element = this._transform(element);
+
+          return {value: element};
+        }
+
+        return {done: true};
+      }
+    };
+  }
+
   /**
    * @callback IterationCallback
    * @param {Object} doc

packages/minimongo/minimongo_tests_client.js

@@ -220,6 +220,17 @@ Tinytest.add('minimongo - cursors', test => {
   // call it again, it still works
   test.length(q.fetch(), 20);
 
+  // iterator
+  count = 0;
+  for (let obj of q) {
+    test.equal(obj.i, count++);
+  };
+  test.equal(count, 20);
+  // call it again, it still works
+  test.length(q.fetch(), 20);
+  // test spread operator
+  test.equal([...q], q.fetch());
+
   // map
   res = q.map(function(obj, i, cursor) {
     test.equal(obj.i, i);