js random number code collection_javascript skills Math

In many cases, random numbers need to be used. Script House has compiled some specific usage and instructions for you.

js random number basics
1. The javascript random number function Math.random()

random (Math.random method)
public static random () : Number

returns a pseudo-random number n, where 0
Returns
Number ─ a number.

Generate a random number within a specified range
The Math.random() method has no parameters and returns a random number between 0 and 1. If you want to generate a random
number between 0 and n, you can Use the following format:

Math.floor(Math.random()*n)
To generate a random number between m~n, you can use:
Math.floor(Math. random()*n) m

javascript Advanced Application of Random Numbers
①Since the creation of JavaScript, many browsers have built-in random number generation methods. For example:
var number = Math.random();
This method produces a floating point number between 0 and 1.
② Based on time, random numbers can also be generated. For example:
var now=new Date();
var number = now.getSeconds();
This will produce an integer from 0 to 59 based on the current time.
var now=new Date();
var number = now.getSeconds()C;
This will produce an integer from 0 to 42 based on the current time.
③Here is an excellent random number generator program that can be used in many fields.

Detailed source reference: http: //www.php.cn/


So how to easily obtain a random number within a specified range? After my comparison, this function of mine is by far the most concise and practical on the Internet
Example code:

[Ctrl A Select all Note: If necessary Introducing external Js requires refreshing before execution]

Code description:

Copy code The code is as follows:

< ;script>
//Declare a random number variable, the default is 1
var GetRandomn = 1;
//Function to get a value in a random range
function GetRandom(n){GetRandomn=Math. floor(Math.random()*n 1)}
//Start the call and get a random number from 1 to 100
GetRandom("100");
//View the output
document. write(GetRandomn)


Isn’t that a pretty concise code? GetRandomn is a random number variable and can be called at will.
Let’s take a random display special effect code:
<script> <br/>//Start now, first get a random number from 1 to 3<br/>GetRandom("3"); <br/>/ /Call items that match random numbers <br/>switch(GetRandomn){ <br/>case 1: <br/>document.write("When the random number is 1, display the script home") <br/>break; <br/>case 2: <br/>document.write("When the random number is 2, www.jb51.net is displayed") <br/>break; <br/>} <br/></script>

Quote part:

1. Starting from 1 to any value
parseInt(Math.random()*upper limit 1);

2. Starting from any value to any value
parseInt(Math.random()*(upper limit-lower limit 1) lower limit);
function fRandomBy(under, over){
switch(arguments. length){
case 1: return parseInt(Math.random()*under 1);
case 2: return parseInt(Math.random()*(over-under 1) under);
default : return 0;
}
}
document.write(fRandomBy(1,100)); //Output a random integer of random numbers within the specified range


The following is to assign different random values ​​to the text box according to the rules [extension]

Copy the code The code is as follows:

1-10: < ;input type="text" />

11-20:

1-100:

51-100:


<script> <br/>window.onload=function(){ <br/>var o=document.getElementsByTagName('input'); <br/>o[0].value=fRandomBy(1,10); <br/>o[1].value =fRandomBy(11,20); <br/>o[2].value=fRandomBy(1,100); <br/>o[3].value=fRandomBy(51,100); <br/>} <br/></script>