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

<p>点击下面的按钮，只要 i 小于 5 就一直循环代码块。</p>
<button onclick="myFunction()">点击这里</button>
<p id="demo"></p>
<script>
function myFunction(){
    var x="",i=0;
    while (i<5){
        x=x + "该数字为 " + i + "<br>";
        i++;
    }
    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>点击下面的按钮，只要 i 小于 5 就一直循环代码块。</p>
<button onclick="myFunction()">点击这里</button>
<p id="demo"></p>
<script>
function myFunction(){
    var x="",i=0;
    do{
        x=x + "该数字为 " + i + "<br>";
        i++;
    }
    while (i<5)  
    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>

<script>
cars=["BMW","Volvo","Saab","Ford"];
var i=0;
for (;cars[i];){
    document.write(cars[i] + "<br>");
    i++;
}
</script>

</body>
</html>

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

<script>
cars=["BMW","Volvo","Saab","Ford"];
var i=0;
while (cars[i]){
    document.write(cars[i] + "<br>");
    i++;
}
</script>

</body>
</html>