# Javascript generates random numbers within a specified range

Source: Internet
Author: User

However, after a small effort, I finally touched the door and solved the problem.
Then, a formula is written, which should disappear. formula:
1. Starting from 1 to any value
Linenum
ParseInt (Math. random () * Upper Limit + 1 );
2. From any value to any value
Linenum
ParseInt (Math. random () * (upper limit-lower limit + 1) + lower limit );
The above formula uses parseInt (), so we need to add 1; if we use Math. ceil (), we do not need to add 1. I am used to writing this...
Directory:
1. Demo 1 (directly generate a random number)
2. DEMO 2 (write as a function to generate a random number)
1. Demo 1 (directly generate a random number)
Linenum
<Script type = "text/javascript">
// <! [CDATA [
Var n = na = nb = nc = '';
N = parseInt (Math. random () * 10 + 1 );
Na = parseInt (Math. random () * (20-11 + 1) + 11 );
Nb = parseInt (Math. random () * 100 + 1 );
Nc = parseInt (Math. random () * (100-51 + 1) + 51 );
Var o = document. getElementsByTagName ('input ');
O [0]. value = n;
O [1]. value = na;
O [2]. value = nb;
O [3]. value = nc;
} // Shawl. qiu script
//]>
</Script>
1-10: <input type = "text"/> <br/>
11-20: <input type = "text"/> <br/>
1-100: <input type = "text"/> <br/>
51-100: <input type = "text"/> <br/>
2. DEMO 2 (write as a function to generate a random number)
Linenum
<Script type = "text/javascript">
// <! [CDATA [
Var o = document. getElementsByTagName ('input ');
O [0]. value = fRandomBy (10 );
O [1]. value = fRandomBy (11, 20 );
O [2]. value = fRandomBy (1,100 );
O [3]. value = fRandomBy (51,100 );
}
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;
}
} // Shawl. qiu script
//]>
</Script>
1-10: <input type = "text"/> <br/>
11-20: <input type = "text"/> <br/>
1-100: <input type = "text"/> <br/>
51-100: <input type = "text"/> <br/>

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