switch方法中使用数字区间

function getCategory(age) {

    var category = "";

    switch (true) {

        case isNaN(age):

            category = "not an age";

            break;

        case (age >= 50):

            category = "Old";

            break;

        case (age <= 20):

            category = "Baby";

            break;

        default:

            category = "Young";

            break;

    };

    return category;

}

getCategory(5);  // 将返回 "Baby"