MIRROR: javascript for 馃悳's, a tiny runtime with big ambitions
1function assert(cond, msg) {
2 if (!cond) throw new Error(msg);
3}
4
5console.log("array prototype and subclassing regression");
6
7assert(Array.isArray(Array.prototype), "Array.prototype should be an array exotic");
8assert(Object.getPrototypeOf(Array.prototype) === Object.prototype, "Array.prototype should inherit from Object.prototype");
9
10class C extends Array {}
11const c = new C(1, 2, 3);
12
13assert(c instanceof C, "Array subclass instances should preserve subclass identity");
14assert(c instanceof Array, "Array subclass instances should still be arrays");
15assert(c.concat(4) instanceof C, "concat should preserve Array subclass");
16assert(c.map(x => x) instanceof C, "map should preserve Array subclass");
17assert(c.filter(() => true) instanceof C, "filter should preserve Array subclass");
18assert(c.slice(0) instanceof C, "slice should preserve Array subclass");
19assert(C.from([1, 2]) instanceof C, "Array.from on subclass should preserve subclass");
20assert(C.of(1, 2) instanceof C, "Array.of on subclass should preserve subclass");
21
22console.log("PASS");