js 注冊時，控制同意按鈕時間

<div style="text-align:center;line-height:36px;">
                      <input name="agree" disabled="disabled" type="submit" id="agree" value="我同意" class="sbutton" />
                    
                        <script type="text/javascript">
                        var secs = 5;
                        var wait = secs * 1000;
                        document.getElementById("agree").value = "同 意(" + secs + ")";
                        document.getElementById("agree").disabled = true;
                        for(i = 1; i <= secs; i++) {
                                window.setTimeout("update(" + i + ")", i * 1000);
                        }
                        window.setTimeout("timer()", wait);
                        function update(num, value) {
                                if(num == (wait/1000)) {
                                        document.getElementById("agree").value = "同 意";
                                } else {
                                        printnr = (wait / 1000) - num;
                                        document.getElementById("agree").value = "同 意(" + printnr + ")";
                                }
                        }
                        function timer() {
                                document.getElementById("agree").disabled = false;
                                document.getElementById("agree").value = "同 意";
                        }
                        </script>
                </div>