JS实现随机数生成算法示例代码

1:

var MT = []; 
var index = 0; 
function initialize_generator(seed) { 
MT[0] = seed; 
for (var i = 1; i < 624; i++) { 
MT[i] = 0xffffffff & (0x6c078965 * (MT[i - 1] ^ (MT[i - 1] >> 30)) + i); 
} 
} 
function generate_numbers() { 
for (var i = 0; i < 624; i++) { 
var y = (MT[i] & 0x80000000) + (MT[(i + 1) % 624] & 0x7fffffff); 
MT[i] = MT[(i + 397) % 624] ^ (y >> 1); 
if (y % 2 != 0) { 
MT[i] ^= 0x9908b0df; 
} 
} 
} 
function extract_number() { 
if (index == 0) { 
generate_numbers(); 
} 
var y = MT[index]; 
y ^= (y >> 11); 
y ^= ((y << 7) & 0x9d2c5680); 
y ^= ((y << 15) & 0xefc60000); 
y ^= (y >> 18); 
index = (index + 1) % 624; 
return y; 
} 
function mt_rand(min, max) { 
return extract_number() % (max - min + 1) + min; 
} 
function test() { 
initialize_generator(new Date().getTime()); 
var test = [0, 0]; 
for (var i = 0; i < 100000; i++) { 
test[mt_rand(0, 1)]++; 
} 
return test; 
}

2:

var random=function(t1,t2,t3){//t1为下限，t2为上限，t3为需要保留的小数位 
function isNum(n){ 
return /^\d+$/.test(n); 
} 
if(!t1 || (! isNum(t1)) ){t1=0;} 
if(!t2 || (! isNum(t2)) ){t2=1;} 
if(!t3 || (! isNum(t3)) ){t3=0;} 
t3 = t3>15?15:t3; // 小数位不能大于15位 
var ra = Math.random() * (t2-t1)+t1,du=Math.pow(10,t3); 
ra = Math.round(ra * du)/du; 
return ra; 
}