<input id="btn" type="submit" value="确定" disabled="disabled" />

<span id="daojishi">10</span>

<script type="text/javascript">

window.setTimeout("YanChi()",1000);

function YanChi()

{

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    //改变span里面的值

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    //判断是否减到了0

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        document.getElementById("btn").removeAttribute("disabled");

        return;

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    window.setTimeout("YanChi()",1000);

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<div>

    <span id="h"></span>

    <span id="m"></span>

    <span id="s"></span>

</div>

<script type="text/javascript">

window.setInterval("Bian()",1000);

function Bian()

{

    var sj = new Date();

        document.getElementById("h").innerText = sj.getHours();

    document.getElementById("m").innerText = sj.getMinutes();

    document.getElementById("s").innerText = sj.getSeconds();

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