输入车牌号判断是否限行

  <script>

        var input = prompt("请输入车牌号:")

        function getLastNum(carNum) {

            var index = carNum.length - 1;// index 赋初始值为最大的索引值

            do {

                var ch = carNum[index]          //最后一位字符

                //charCodeAt 获取对心位置上字符的Unicode码

                //0-9 = 48-57

                if (ch.charCodeAt() >= 48 && ch.charCodeAt() <= 57) {

                    return ch

                }

                index--;

            } while (index >= 0)

        }

        var lastNum = getLastNum(input)

        console.log(lastNum)

        var date = new Date()

        var week = date.getDay()    //获取当前周几

        var hour = date.getHours()  //获取当前时间

        if (week == 6 || week == 0) {

            alert("周六,周日全天不限行")

        } else {

            if (hour < 7 || hour > 21) {

                alert("早上7点之前和晚上21点后不限行")

            } else {

                // 1 1和6

                // 2 2.7

                // week=     1   2   3  4  5  

                // week%5 =  1   2   3  4  0

                // lastNum   1、6    2、7  3、8

                // lastNum%5=1    2  3  4  0

                week = week % 5

                lastNum = lastNum % 5

                if (week == lastNum) {

                    alert("车辆限行")

                } else {

                    alert("车辆不限行")

                }

            }

        }

   </script>