Javascript argumentsテスト

次のテストコードに示すように、argumentsとメソッドパラメータの対応する変化動作は、javascriptの構文定義に従うものではありません.パラメータが値で渡されたり、他の基礎言語ルールで導出されたりすることはできません.
しかしargumentsを利用すると,多くの有用な機能を実現することができ,具体的な例はMDN上のこのキーワードについての説明を参照することができる.

!function(a, b, c, d, e) {
    a = 4;
    console.log("After set a = 4, arguments[0] is", arguments[0]);

    a = undefined;
    console.log("After set a = undefined, arguments[0] is", arguments[0]);

    a = 4;
    console.log("After set a = 4 again, arguments[0] is", arguments[0]);

    arguments[1] = 5;
    console.log("After set arguments[1] = 5, b is", b);

    arguments[1] = undefined;
    console.log("After set arguments[1] = undefined, b is", b);

    arguments[1] = 5;
    console.log("After set arguments[1] = 5 again, b is", b);

    delete arguments[2];
    console.log("After delete arguments[2], c is", c);
    arguments[2] = 6;
    console.log("After set arguments[2] = 6, c is", c);

    arguments[3] = 7;
    console.log("After change arguments[3] from undfined to 7, d is", d);

    e = 8;
    console.log("After change e from undfined to 8, arguments[4]:", arguments[4]);
}(1, 2, 3);

//     
// After set a = 4, arguments[0] is 4
// After set a = undefined, arguments[0] is undefined
// After set a = 4 again, arguments[0] is 4
// After set arguments[1] = 5, b is 5
// After set arguments[1] = undefined, b is undefined
// After set arguments[1] = 5 again, b is 5
// After delete arguments[2], c is 3
// After set arguments[2] = 6, c is 3
// After change arguments[3] from undfined to 7, d is undefined
// After change e from undfined to 8, arguments[4]: undefined