先前我寫了一篇PHP的常用函式庫function.php，裡面有倆個函式 getItemId 和 getRandNumber ，今天就看看用Js改寫之後是怎樣的：

/**
 * 生成itemId
 * @return string
 */
function getItemId() {
    var myDate = new Date();
    var hour = (Math.ceil((myDate - new Date(myDate.getFullYear().toString())) / (24 * 60 * 60 * 1000)) + 1) * 24 + myDate.getHours();

    var num = 4 - hour.length;
    var str = '';
    if (num > 0) {
        for (var i = 0; i < num; i++) {
            str += '0';
        }
    }
    str += hour;
    var start = myDate.getFullYear().toFixed().slice(-2);
    return start + str + getRandNumber(10);
}

/**
 * 生成固定長度的隨機數
 *
 * @param int $length
 * @return string
 */
function getRandNumber(number) {
    var str = "",
        arr = ['0', '1', '2', '3', '4', '5', '6', '7', '8', '9'];

    for (var i = 0; i < number; i++) {
        pos = Math.round(Math.random() * (arr.length - 1));
        str += arr[pos];
    }
    return str;
}

console.log(getItemId());
console.log(getRandNumber(6));