Array#copy-test.js

    // 以下の assert は全部通る。

    let a1 = [{}, 1, 2];
    let a2 = a1.concat();

    assertEqual('A0', false, function () a1 === a2);
    assertEqual('A1', false, function () a1 === ({}));
    assertEqual('A2', true,  function () a1[0] === a2[0]);

    let b1 = [{}, 1, 2];
    let b2 = b1.concat();

    b1[0]['hoge'] = 'moge';

    assertEqual('B0', false, function () b1 === b2);
    assertEqual('B1', true, function () b1[0] === b2[0]);
    assertEqual('B2', 'moge', function () b1[0].hoge);
    assertEqual('B3', 'moge', function () b2[0].hoge);

    let c1 = [['moge'], 1, 2];
    let c2 = c1.concat();

    c1[0][0] = 'hage';

    assertEqual('C0', false, function () c1 === c2);
    assertEqual('C1', true, function () c1[0] === c2[0]);
    assertEqual('C2', 'hage', function () c1[0][0]);
    assertEqual('C3', 'hage', function () c2[0][0]);