JS generation [N,m] random number

First, the preparation of knowledge

Math.ceil (); Rounding up.

Math.floor (); Rounding down.

Math.Round (); Rounded.

Math.random (); A pseudo-random number between 0.0 ~ 1.0. "Contains 0 does not contain 1"//For example 0.8647578968666494

Math. Ceil      (Math.random () *10); Gets a random integer from 1 to 10, with a minimum probability of 0.

Math. round   (Math.random ()); A random integer from 0 to 1 can be obtained evenly.

Math. Floor  (Math.random () *10); A random integer from 0 to 9 can be obtained evenly.

Math. round  (Math.random () *10); Basic equalization Gets a random integer from 0 to 10, where the probability of getting a minimum of 0 and a maximum of 10 is less than half .

Because the result in 0~0.4 is 0, 0.5 to 1.4 is 1 ... 8.5 to 9.4 is 9, 9.5 to 9.9 is 10. So there is only half of the other numbers in the distribution between the tail.

Ii. generating a random integer [n,m]

function function: Generates a random integer [N,m].

Useful when JS generates a verification code or randomly selects an option.

//Generate random numbers from Minnum to Maxnumfunction Randomnum (minnum,maxnum) {switch (arguments.length) {case 1: return parseint (Math.random () *minnum+1,10break; case 2: return parseint ( Math.random () * (maxnum-minnum+1) +minnum,10break; default: return 0; break 

Process Analysis:

Math.random () generates the number of [0,1], so

Math.random () The number of {0,5) generated.

Usually expect to get an integer, so we need to deal with the resulting results.

parseint (), Math.floor (), Math.ceil (), and Math.Round () all have integers.

Both the parseint () and Math.floor () results are rounded down.

So Math.random () is generated by a random integer [0,4].

So generate [1,max] random number, the formula is as follows:

max-Desired maximum value parseint (Math.random () *max,10) +1; Math.floor (Math.random () *max) +1; Math.ceil (Math.random () *max);  

So generate [0,max] to any number of random numbers, the formula is as follows:

max-Desired maximum value parseint (Math.random () * (max+1); Math.floor (Math.random () * (max+1)); 

So I want to generate [Min,max] random numbers, the formula is as follows:

Max-expected maximum // min-Desired minimum value parseint (Math.random () * (max-min+1) +min,10); Math.floor (Math.random () * (max-min+1) +min);   

JS generation [N,m] random number