自动生成的文本框中的数字

i JS代码，该代码在文本框中生成15位数字，我想将生成的数字减少到5或6位。请帮助我。

<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
    <title></title>
    <script type="text/javascript">
        now = new Date();
        randomNum = '';
        randomNum += Math.round(Math.random() * 9);
        randomNum += Math.round(Math.random() * 9);
        randomNum += now.getTime();
        window.onload = function () {
            document.getElementById("txt_usrid").value = randomNum;
        }
    </script>
</head>
<body>
    <form id="form1" runat="server">
    <div>
        <input type="text" tooltip="User Id" id="txt_usrid"/>
    </div>
    </form>
</body>
</html>

尝试使用Array#slice

now = new Date();
randomNum = '';
randomNum += Math.round(Math.random() * 9);
randomNum += Math.round(Math.random() * 9);
randomNum += now.getTime().toString().slice(-4);
window.onload = function() {
  document.getElementById("txt_usrid").value = randomNum;
}

<form id="form1" runat="server">
  <div>
    <input type="text" tooltip="User Id" id="txt_usrid" />
  </div>
</form>

您可以用substr

将其串联

<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
    <title></title>
    <script type="text/javascript">
        now = new Date();
        randomNum = '';
        randomNum += Math.round(Math.random() * 9);
        randomNum += Math.round(Math.random() * 9);
        randomNum += now.getTime();
        window.onload = function () {
            document.getElementById("txt_usrid").value = randomNum.substr(0,5); // HERE ;)
        }
    </script>
</head>
<body>
    <form id="form1" runat="server">
    <div>
        <input type="text" tooltip="User Id" id="txt_usrid"/>
    </div>
    </form>
</body>
</html>

做到这一点的最有效方法是从.getTime()检索最后3个数字，并将它们附加到2个随机整数。由于这些数字与当前日期的毫秒相关，它们应该意味着生成的数字的外观是随机化的 - 尽管显然不是真正的随机数。尝试以下操作：

now = new Date();
randomNum = '';
randomNum += Math.round(Math.random() * 9);
randomNum += Math.round(Math.random() * 9);
randomNum += now.getTime().toString().slice(-3);
window.onload = function() {
  document.getElementById("txt_usrid").value = randomNum;
}

<form id="form1" runat="server">
  <div>
    <input type="text" tooltip="User Id" id="txt_usrid" />
  </div>
</form>

<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
    <title></title>
    <script type="text/javascript">
        now = new Date();
        randomNum = '';
        randomNum += Math.round(Math.random() * 9);
        randomNum += Math.round(Math.random() * 9);
        randomNum += Math.round(now.getTime() / 1000000000); // it was creating the number of milliseconds since 1970/01/01 so it should be less
        randomNum = Math.round(Math.random() * randomNum);
        window.onload = function () {
            document.getElementById("txt_usrid").value = randomNum;
        }
    </script>
</head>
<body>
    <form id="form1" runat="server">
    <div>
        <input type="text" tooltip="User Id" id="txt_usrid"/>
    </div>
    </form>
</body>
</html>

更新：生成更多随机数

now = new Date();
randomNum = '';
randomNum += Math.round(Math.random() * 9);
randomNum += Math.round(Math.random() * 9);
randomNum += now.getTime().toString().slice(-3);
window.onload = function() {
  document.getElementById("txt_usrid").value = randomNum;
}

<form id="form1" runat="server">
  <div>
    <input type="text" tooltip="User Id" id="txt_usrid" />
  </div>
</form>

now = new Date();
randomNum = '';
randomNum += Math.round(Math.random() * 9);
randomNum += Math.round(Math.random() * 9);
randomNum += now.getTime().toString().slice(-3);
window.onload = function() {
  document.getElementById("txt_usrid").value = randomNum;
}

<form id="form1" runat="server">
  <div>
    <input type="text" tooltip="User Id" id="txt_usrid" />
  </div>
</form>

try string.substring((方法：

now = new Date();
randomNum = '';
randomNum += Math.round(Math.random() * 9);
randomNum += Math.round(Math.random() * 9);
randomNum += now.getTime();
console.log(randomNum.substring(5, 11));

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