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window.addEventListener("load",function(){

    var oOpenBaiduBtn = this.document.getElementById("openBaiduBtn");
    var oBaiduWin = null;
    oOpenBaiduBtn.addEventListener("click",function(){
        oBaiduWin = window.open("http://www.baidu.com", "_blank");
    });

    var oCloseBaiduBtn = this.document.getElementById("closeBaiduBtn");
    oCloseBaiduBtn.addEventListener("click",function(){
        oBaiduWin.close();
    });

    var oOpenNewBtn = this.document.getElementById("openNewBtn");
    var oNewWin = null;
    oOpenNewBtn.addEventListener("click",function(){
        oNewWin = window.open();
    })

    var oChangeNewBtn = this.document.getElementById("changeNewBtn");
    oChangeNewBtn.addEventListener("click",function(){
        oNewWin.document.title = "新窗口";
        oNewWin.document.body.innerHTML = "<div><p><string>Hi</strong>,I'm a new window</p></div>";
        oNewWin.document.body.style.color = "blue";
    })

    var oCloseNewBtn = this.document.getElementById("closeNewBtn");
    oCloseNewBtn.addEventListener("click",function(){
        oNewWin.close();
    })

    var oAlerBtn = this.document.getElementById("alertBtn");
    oAlerBtn.addEventListener("click",function(){
        window.alert("我是告警窗口");
    });

    var oConfirmBtn = this.document.getElementById("confirmBtn");
    oConfirmBtn.addEventListener("click",function(){
        var bConfirmed = window.confirm("你要不要打开百度？");
        if(bConfirmed) {
            window.open("http://www.baidu.com");
        }
    });

    var oPromptBtn = this.document.getElementById("promptBtn");
    oPromptBtn.addEventListener("click",function(){
        var strText = window.confirm("请输入提示：");
        if(strText) {
            var oText = window.document.getElementById("text");
            oText.innerHTML = strText;
        }
    });

    var oStartTimerBtn = this.document.getElementById("startTimer");
    var oStopTimerBtn = this.document.getElementById("stopTimer");
    var oTimerBox = this.document.getElementById("timerBox");
    var oTimer;

    oStartTimerBtn.addEventListener("click",function(){
        if(oTimer){
            window.clearTimeout(oTimer);
        }
        oTimer = window.setTimeout(function(){
            oTimerBox.style.backgroundColor = "blue";
        },2000);
    });
    
    oStopTimerBtn.addEventListener("click",function(){
        if(oTimer){
            window.clearTimeout(oTimer);
        }
    });

    var oStartIntervalBtn = this.document.getElementById("startInterval");
    var oStopIntervalBtn = this.document.getElementById("stopInterval");
    var oIntervalBox = this.document.getElementById("intervalBox");
    var oIntervalText = this.document.getElementById("intervalText");
    var oInterval;
    var count = 5;
    oIntervalText.innerHTML = count;

    function changeColor(){
        var colors = ["red","green","pink","yellow","lightskyblue"];
        if(count>0){
            count--;
            oIntervalBox.style.backgroundColor = colors[count];
            oIntervalText.innerHTML = count;
        }
        else{
            count = 5;
        }
    }

    oStartIntervalBtn.addEventListener("click",function(){
        if(oInterval){
            window.clearInterval(oInterval);
        }
        oInterval = window.setInterval(changeColor,1000);
        });
    
    
    oStopIntervalBtn.addEventListener("click",function(){
        if(oInterval){
            window.clearInterval(oInterval);
        }
    });
})

<!DOCTYPE html> 
<html>
<head>
    <meta charset="utf-8" />
    <title></title>
    <script>
    </script>
</head>
<body>
    <div>
        <button id="openBaiduBtn">打开百度</button>
        <button id="closeBaiduBtn">关闭百度</button>
    </div>
    <br/>
    <div>
        <button id="openNewBtn">打开空白页面</button>
        <button id="changeNewBtn">绘制空白页面</button>
        <button id="closeNewBtn">关闭空白页面</button>
    </div>
    <br/>
    <div>
        <button id="alertBtn">打开告警窗口</button>
        <button id="confirmBtn">打开确认窗口</button>
        <br/>
        <div>
            <button id="promptBtn">打开提示窗口</button>
            <label>提示文字:</label><p id="text"></p>
        </div>
         <br/>
    <div>
        <button id = "startTimer">开始</button>
        <button id = "stopTimer">结束</button>
        <div id="timerBox"></div>
    </div>
    <br/>
    <div>
        <button id = "startInterval">开始</button>
        <button id = "stopInterval">结束</button>
        <div id="intervalBox"></div>
        <span>倒计时：</span><span id="intervalText"></span>
    </div> 
    </div>
</body>
</html>

#timerBox {
    width: 100px;
    height: 100px;
    border : 1px solid black;
    background-color: lightblue;
}

#intervalBox {
    width: 100px;
    height: 100px;
    border : 1px solid black;
    background-color:royalblue;
}