获取随机时间,且不同时间段的概率不等的计算方法

        var rNum = Math.random();
        if(rNum<0.8) {
            return 1
        }
        else {
            return 2
        }

function getNumber(a,b){
    var r = Math.random()*(b-a);
    //0-(b-a)
    var mini = r - Math.floor(r);
    var big = Math.floor(r);
    if((big%2==0 && mini<0.4) || (big%2==1)) {
        r = Math.floor(r)
    }
    else {
        r = Math.ceil(r)
    }
    if((r+a)%2==0){
        shuang+=1;
    }
    else if ((r+a)%2!==0){
        dan+=1
    }
    return shuang/dan;

}

var dan = 0;
var shuang = 0;
for(var i=0; i<100; i++){
    console.log(getNumber(62,10000001))
}

    /***************t1-t2随机取整***************/
    function getRandom(t1,t2){
        var r = Math.round(Math.random()*(t2-t1));
        return r+t1;
    }

    /***************arr数组中随机取一项***************/
    function getRandomArr(arr){
        var index = getRandom(0,arr.length-1);
        return arr[index]
    }

    /***************arr数组中随机取一项***************/
    function getTimeArr(t1,t2) {
        var arr1 = [];
        var arr2 = [];
        function pushTime(){
            var t = getRandom(t1,t2);
            var h = new Date(t).getHours();
            if(h>=8 && h<=22){
                if(arr1.length<4) arr1.push(t);
                return judgeArr()
            }
            else {
                if(arr2.length<1) arr2.push(t);
                return judgeArr()
            }
        }
        function judgeArr(){
            if(arr1.length==4 && arr2.length==1){
                Array.prototype.push.apply(arr1,arr2);
                return arr1
            }
            else {
                return pushTime()
            }
        }
        return pushTime();
    }

    var date1 = new Date(2015,0,1,0,0,0,0).getTime();
    var date2 = new Date(2015,1,1,0,0,0,0).getTime();

    var time = getRandomArr(getTimeArr(date1,date2));

    alert(new Date(time).getHours());