<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<script>
function myFunction(){
    alert("你好，我是一个警告框！");
}
</script>
</head>
<body>

<input type="button" onclick="myFunction()" value="显示警告框" />

</body>
</html>

<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>菜鸟教程(runoob.com)</title>
</head>
<body>

<p>点击按钮，显示确认框。</p>
<button onclick="myFunction()">点我</button>
<p id="demo"></p>
<script>
function myFunction(){
    var x;
    var r=confirm("按下按钮!");
    if (r==true){
        x="你按下了\"确定\"按钮!";
    }
    else{
        x="你按下了\"取消\"按钮!";
    }
    document.getElementById("demo").innerHTML=x;
}
</script>

</body>
</html>

<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>菜鸟教程(runoob.com)</title>
</head>
<body>

<p>点击按钮查看输入的对话框。</p>
<button onclick="myFunction()">点我</button>
<p id="demo"></p>
<script>
function myFunction(){
    var x;
    var person=prompt("请输入你的名字","Harry Potter");
    if (person!=null && person!=""){
        x="你好 " + person + "! 今天感觉如何?";
        document.getElementById("demo").innerHTML=x;
    }
}
</script>

</body>
</html>

<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>菜鸟教程(runoob.com)</title>
</head>
<body>

<p>点击按钮在弹窗总使用换行。</p>
<button onclick="myFunction()">点我</button>
<p id="demo"></p>
<script>
function myFunction(){
    alert("Hello\nHow are you?");
}
</script>

</body>
</html>