怎样通过点击随机的按钮让它在文本框中自动产生一个随机数

Question

<form name="form1" method="post" action="">
  <table width="40%"  border="0">
    <tr>
      <td width="23%" align="center">a</td>
      <td width="77%"><input type="text" name="u"></td>
    </tr>
    <tr>
      <td align="center">b</td>
      <td><input type="text" name="p">
      <input type="button" name="Submit1" value="随机" onclick="show()"></td>
    </tr>
    <tr align="center">
      <td colspan="2"><input type="submit" name="Submit2" value="提交"></td>
    </tr>
  </table>
</form>
<script language=javascript>
function show()
{
var str="0123456789abcdefghijklmnopqrstuvwxyz"
var result=""
for(var i=0;i<6;i++)
{
var temp=Math.floor(Math.random()*36)
result+=str.charAt(temp)
}
document.getElementById("p").value=result
}
</script>

Answer 1

稍微修改一下，自定义长度<form name="form1" method="post" action="">
  <table width="40%"  border="0">
    <tr>
      <td width="23%" align="center">a</td>
      <td width="77%"><input type="text" name="u"></td>
    </tr>
    <tr>
      <td align="center">b</td>
      <td><input type="text" name="p">
      <input type="button" name="Submit1" value="随机" onclick="show(6)"></td>
    </tr>
    <tr align="center">
      <td colspan="2"><input type="submit" name="Submit2" value="提交"></td>
    </tr>
  </table>
</form>
<script language=javascript>
function show(l)
{
var str="0123456789abcdefghijklmnopqrstuvwxyz"
var result=""
for(var i=0;i<l;i++)
{
var temp=Math.floor(Math.random()*36)
result+=str.charAt(temp)
}
document.getElementById("p").value=result
}
</script>

Answer 2

<script>
var str = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
function genStr(obj, len) {
obj.value = "";
for (i=0; i<len ;i++)
obj.value += str.charAt(Math.floor(Math.random() * str.length));
}
</script>
<form name="form1" method="post" action="">
  <table width="40%"  border="0">
    <tr>
      <td width="23%" align="center">a</td>
      <td width="77%"><input type="text" name="u"></td>
    </tr>
    <tr>
      <td align="center">b</td>
      <td><input type="text" name="p">
      <input type="button" name="Submit" value="随机" onclick="genStr(form1.u, 10); genStr(form1.p, 10);"></td>
    </tr>
    <tr align="center">
      <td colspan="2"><input type="submit" name="Submit2" value="提交"></td>
    </tr>
  </table>
</form>