javascript数组自定义属性

Question

如下，关于javascript中数组的自定义属性，应该怎么理解

var ary = ["a", "b", "c"];

ary.name = "tom";

ary.age = 3;

console.log(ary); // ["a", "b", "c", name: "test"]

console.log(ary.length); // 3

console.log(Array.isArray(ary)); // true

console.log(ary.name); // "tom"

console.log(ary.age); // 3

ary.forEach(function (v) {

    console.log(v); // 依次打印 a b c

});

for (var prop in ary) {

    console.log(ary[prop]); // 依次打印 tom 3

}