| // Copyright 2018 the V8 project authors. All rights reserved. | |
| // Use of this source code is governed by a BSD-style license that can be | |
| // found in the LICENSE file. | |
| const arr = [1, , 3]; | |
| function mapper(x) { | |
| Array.prototype[1] = 2; | |
| return x + 1; | |
| } | |
| // We force a direct iteration (using the array length, not the iterator | |
| // protocol). The mapper function gets called during this iteration, not in a | |
| // separate one. Hence when index 1 is read, 2 is retrieved from the prototype | |
| // and incremented to 3. | |
| Array.prototype[Symbol.iterator] = undefined; | |
| assertArrayEquals([2, 3, 4], Uint16Array.from(arr, mapper)); |