JS generates a random number of the specified bits

< HTML >
<script>//Gets the random number of the specified number of bits function getrandom (num) {    var random = Math.floor ((Math.random () +math.floor ( Math.random () *9+1)) *math.pow (10,num-1));} Call the random number function to generate a 10-digit random number getrandom (10);
</script></html>

Implementation of the idea (at the end of the code process and the results of the operation) to obtain a 10-bit random number as an example:

1, Math.random () function can get 0 to 1 decimal, Math.pow (10,10) function is equivalent to 10 10, the Math.floor () function is rounded down to remove the decimal place;

2, the combination can obtain a 10-bit random number: Math.floor (Math.random () *math.pow (10,10));

3, however, if the first decimal digit of Math.randow () is 0, it is possible to obtain a 9-bit random number;

4, the Math.randow () plus 1, excluding the first decimal place for the case of 0, the corresponding power operation minus one

Math.floor ((Math.random () +1)) *math.pow (10,9));

This will get a random number of 10 bits, but all will start with 1;

5, in order to start also can randomly take number, can replace 1 with Math.floor (Math.random () *9+1);

6. The final code is as follows:

Math.floor ((Math.random () +math.floor (Math.random () *9+1)) *math.pow (10,9));

So we can get a completely random 10-bit random number.

Gets the random number, the first digit of the decimal may be 0console.log (Math.random ());//Gets a 10-bit random number, if the decimal first bit is 0 then only 9 digits Console.log (Math.floor (Math.random () * Math.pow (10,10)));//random number +1, solving the situation where the first digit of the decimal is 0//But the first digit that causes the random number is always 1console.log (Math.floor ((Math.random () +1) *math.pow (10,9 )), or//The random number +1 is also changed to random plus the number between 1~9, solve the first bit is always 1 problem Console.log (Math.floor ((Math.random () +math.floor (Math.random () *9+1) * Math.pow (10,9)); Chrome browser Debug Run results-----------------------------------------------------------------------------get random numbers, The first digit of the decimal may be 0:0.097574709201919 to get 10-bit random numbers, if the decimal number first is 0 then only 9 digits: 623721160 random number + 1, solve the situation where the first digit of the decimal is 0: But the first digit of the random number is always 1:1,242,782,126, the random number +1 is also changed to random plus the number between 1~9, solving the problem that the first bit is always 1:7671051679

JS generates a random number of the specified bits