apply-test.js

import { NativeArray } from '../../lib/mixins/array';
import { AbstractTestCase, moduleFor } from 'internal-test-helpers';

class ArrayPrototypeExtensionSelfReferenceTests extends AbstractTestCase {
  '@test should not create non-Symbol, enumerable properties that refer to itself'() {
    // Don't want to pollute Array.prototype so we make our own to extend
    class ThrowAwayArray extends Array {}

    // Extend our throw-away prototype (like EXTEND_PROTOTYPES.Array would)
    NativeArray.apply(ThrowAwayArray.prototype);

    // Create an instance to test
    let obj = new ThrowAwayArray();

    // Make sure we have an array-like thing & avoid the zero assertion problem is there are no enumerable properties
    this.assert.strictEqual(obj.length, 0);

    // Make sure that no enumerable properties refer back to the object (creating a cyclic structure)
    for (let p in obj) {
      this.assert.notStrictEqual(
        obj[p],
        obj,
        `Property "${p}" is an enumerable part of the prototype
        so must not refer back to the original array.
        Otherwise code that explores all properties,
        such as jQuery.extend and other "deep cloning" functions,
        will get stuck in an infinite loop.
        `.replace(/\s+/g, ' ')
      );
    }
  }
}

moduleFor(`NativeArray: apply`, ArrayPrototypeExtensionSelfReferenceTests);