console 命令行工具 X clear

console

function alertSecond(){
    alert("第二次");
}
function changeColor(){
    if(this.style.color=="red"){
        this.style.color="black";
    }else{
        this.style.color="red";
    }
}
function changeBackgroundColor() {
    if (this.style.backgroundColor=="lightskyblue") {
        this.style.backgroundColor="white";
    }
    else {
         this.style.backgroundColor="lightskyblue";
    }
   
} 

window.onload = function () 
{
    var oBtn = document.getElementById("btn");
    oBtn.onclick = function () {
        alert("第1次");
    };
    oBtn.onclick = function () {
        alert("第2次");
    };
    oBtn.onclick = function () {
        alert("第1次");
        alert("第2次");
        alert("第3次");
    };

    var oBtn=document.getElementById("listenBtn");
    
    oBtn.addEventListener("click",function(){
        alert("第1次");
    },false);
    oBtn.addEventListener("click",alertSecond,false);
    oBtn.removeEventListener("click",alertSecond,false);
    
    var oPContent=document.getElementById("content");
    oPContent.addEventListener("click",changeColor,false);
    oPContent.addEventListener("click",changeBackgroundColor,false);

    var oBtn=document.getElementById("removeBtn");

    oBtn.addEventListener("click",function(){
        oPContent.removeEventListener("click",changeColor,false);
    },false);

    var oPContent1=document.getElementById("content1");
    oPContent1.onclick=changeColor;

    var oBtn1=document.getElementById("removeBtn1");
    
    oBtn1.addEventListener("click",function(){
        oPContent.onclick=null;
    },false);

    document.addEventListener("keydown",function(event){
        console.log(event.type);
        if(event.shiftKey||event.altKey||event.ctrlKey){
            console.log("你按下了shift,alt或者ctrl");
        }
        console.log("你按下了"+event.keyCode);
    });
    document.addEventListener("keyup",function(event){
        console.log(event.type);
        console.log("你松开了"+event.keyCode);
    });
}

<!DOCTYPE html> 
<html>
<head>
    <meta charset="utf-8" />
    <title></title>
    <script>
      
    </script>
</head>
<body>
    <input id="btn" type="button" value="按钮"/>
    <br/>
    <br/>
    <input id="listenBtn" type="button" value="监听按钮"/>
    <br/>
    <div>
        <p id="content">中国</p>
        <button id="removeBtn">解除</button>
    </div>

    <div>
        <p id="content1">中国</p>
        <button id="removeBtn1">解除</button>
    </div>
</body>
</html>