added keys method (#692)

devs/run-tests/24arraymap.ts

@@ -204,6 +204,22 @@ function testArraySort() {
     assert(mixed.join() === "2,5,9,apple,banana,cherry", "sort5")
 }
 
+function testArrayKeys() {
+    const sparseArray = ['a', undefined , 'c']
+    const array = ["a", "b", "c"]
+
+    assert(joinIterable(array.keys()) === '0,1,2', "arrayKeys")
+    assert(joinIterable(sparseArray.keys()) === '0,1,2', "sparseArrayKeys")
+
+    function joinIterable(iterator: IterableIterator<number>): string {
+        const values:number[] = [];
+        for (const key of iterator) {
+            values.push(key)
+        }
+        return values.join();
+    }
+}
+
 testArraySome()
 testArrayEvery()
 testArrayFill()
@@ -219,3 +235,4 @@ testArrayIncludes()
 testArrayAt()
 testArrayWith()
 testArraySort()
+testArrayKeys()

packages/core/src/array.ts

@@ -210,6 +210,11 @@ Array.prototype.sort = function <T>(compareFn?: (a: T, b: T) => number) {
     return this
 }
 
+Array.prototype.keys = function () {
+    console.log ('KEYS', this.length);
+    return Array(this.length).fill(0).map((_, i) => i);
+}
+
 Buffer.prototype.set = function (other: Buffer, trgOff?: number) {
     if (!trgOff) trgOff = 0
     this.blitAt(trgOff, other, 0, other.length)

packages/core/src/corelib.d.ts

@@ -430,6 +430,11 @@ interface Array<T> {
      * ```
      */
     sort(compareFn?: (a: T, b: T) => number): this
+
+    /**
+     * Returns an iterable of keys in the array
+     */
+    keys(): IterableIterator<number>;
 }
 
 interface ArrayConstructor {