1 <!DOCTYPE html> 2 <html> 3 <head> 4 ????<meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> 5 ????<title></title> 6 ????<meta charset="utf-8" /> 7 ????<script> 8 ????????//取值范围min-max; 9 ????????//能随机到min和max[min,max]10 ????????function rnd(min, max) {11 ????????????var tmp = min;12 ????????????if (max < min) { min = max; max = tmp; }//交换值13 ????????????return Math.floor(Math.random() * (max - min + 1) + min); //向下取整14 ????????}15 ????????for (i = 0; i < 10; i++) {16 ????????????// document.write(rnd(5, 7)+"<br/>");17 ????????}18 19 ????</script>20 ????<script>21 ????????//取值范围min-max;22 ????????//能随机到min 不能随机到max ??[min,max)23 ????????function rnd(min, max) {24 ????????????var tmp = min;25 ????????????if (max < min) { min = max; max = tmp; }//交换值26 ????????????return Math.floor(Math.random() * (max - min) + min); //向下取整27 ????????}28 ????????for (i = 0; i < 10; i++) {29 ????????????// document.write(rnd(1,5) + "<br/>");30 ????????}31 ????</script>32 ????<script>33 ????????//取值范围min-max;34 ????????//能随机到max 不能随机到min ??(min,max]35 ????????function rnd(min, max) {36 ????????????var tmp = min;37 ????????????if (max < min) { min = max; max = tmp; }//交换值38 ????????????return Math.ceil(Math.random() * (max - min) + min); //向上取整39 ????????}40 ????????for (i = 0; i < 10; i++) {41 ???????????// document.write(rnd(1, 5) + "<br/>");42 ????????}43 ????</script>44 45 ????<script>46 ????????//取值范围min-max;47 ????????//不能随机到min和max(min,max)48 ????????function rnd(min, max) {49 ????????????var tmp = min;50 ????????????var temp;51 ????????????if (max < min) { min = max; max = tmp; }//交换值52 ????????????temp = Math.floor(Math.random() * (max - min + 1) + min); //向下取整53 ????????????if (min == temp) {54 ????????????????return min + 1;55 ????????????} else { return temp; }56 ????????}57 ????</script> 58 ????<!-- 59 ????????var a = max/min; ?????????????a = 7;60 ????????var xs = (a - 1); ????????????xs = 7/1 - 1 = 6; 61 ????????var x=(max-1.0001)/min-1 ?????x ((7-1.0001)/1)-1 = 5.9995; ????x/xs = 5.9995/6 = 0.9999162 ????????(7 - 1) * (0.999 *(x/xs))) ?= 6.9999 ??向上取整 ??==663 ?????????1 + 6 * (0.1 *(x/xs)) ?= 1.09991 ??向上取整 ?????==264 ????????原理是 最小数 + 最小数{(a-1)(随机数)(缩小比例x/xs)}65 ????????1(1+6)(0.999*0.9999) = ??????66 ????????????????当min=1时候; a= max;67 ????????-->68 ????<script>69 ????????function rnd(min,max){70 ????????????var a = max / min;71 ????????????var xs = (a - 1);72 ????????????var x = (max - 1.0001) / min - 1;73 ????????????return Math.ceil(min * (1 + (a - 1) * (Math.random() *(x/xs))));74 ????????}75 ????????for (i = 0; i < 100; i++) {76 ????????????document.write("xxx开区间" + rnd(1,7) + "<br/>");77 ????????}78 79 ????</script>80 </head>81 <body>82 83 </body>84 </html>js 随机数
原文地址：http://www.cnblogs.com/enych/p/7644924.html