alert(Math.min(2,4,3,6,3,8,0,1,3));              //最小值
alert(Math.max(4,7,8,3,1,9,6,0,3,2));         //最大值

alert(Math.ceil(25.9));                   //26
alert(Math.ceil(25.5));                   //26
alert(Math.ceil(25.1));                   //26
alert(Math.floor(25.9));                  //25
alert(Math.floor(25.5));                  //25
alert(Math.floor(25.1));                  //25
alert(Math.round(25.9));                     //26
alert(Math.round(25.5));                     //26
alert(Math.round(25.1));                     //25

for (var i = 0; i<10;i ++) {
    document.write(Math.floor(Math.random() * 10 + 5));       //5-14之间的任意数
    document.write('<br />');
}

function selectFrom(lower, upper) {
    var sum = upper - lower + 1;                      //总数-第一个数+1
    return Math.floor(Math.random() * sum + lower);
}
for (var i=0 ;i<10;i++) {
    document.write(selectFrom(5,10));                 //直接传递范围即可
    document.write('<br />');
}