esnext.string.at-alternative.js

// TODO: disabled by default because of the conflict with another proposal
import { STRICT } from '../helpers/constants';

QUnit.test('String#at', assert => {
  const { at } = String.prototype;
  assert.isFunction(at);
  assert.arity(at, 1);
  assert.name(at, 'at');
  assert.looksNative(at);
  assert.nonEnumerable(String.prototype, 'at');
  assert.same('1', '123'.at(0));
  assert.same('2', '123'.at(1));
  assert.same('3', '123'.at(2));
  assert.same(undefined, '123'.at(3));
  assert.same('3', '123'.at(-1));
  assert.same('2', '123'.at(-2));
  assert.same('1', '123'.at(-3));
  assert.same(undefined, '123'.at(-4));
  assert.same('1', '123'.at(0.4));
  assert.same('1', '123'.at(0.5));
  assert.same('1', '123'.at(0.6));
  assert.same('1', '1'.at(NaN));
  assert.same('1', '1'.at());
  assert.same('1', '123'.at(-0));
  assert.same('\uD842', '𠮷'.at());
  assert.same('1', at.call({ toString() { return '123'; } }, 0));
  if (STRICT) {
    assert.throws(() => at.call(null, 0), TypeError);
    assert.throws(() => at.call(undefined, 0), TypeError);
  }
});