--循环输出标题

<p>Click the button to loop from 1 to 6, to make HTML headings.</p>

<button onclick="myFunction()">Try it</button>

<div id="demo"></div>

<script>

function myFunction()

{

var x="",i;

for (i=1; i<=6; i++)

{

x=x + "<h" + i + ">Heading " + i + "</h" + i + ">";

}

document.getElementById("demo").innerHTML=x;

}

</script>

// while 循环

<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> 

 // do while

<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>

//break中断循环

<p>点击按钮，测试带有 break 语句的循环。</p>

<button onclick="myFunction()">点击这里</button>

<p id="demo"></p>

<script>

function myFunction(){

 var x="",i=0;

 for (i=0;i<10;i++){

  if (i==3){

       break;

   }

     x=x + "该数字为 " + i + "<br>";

    }

 document.getElementById("demo").innerHTML=x;

}

</script>

 //continue跳过本次循环，继续下个循环

<p>点击下面的按钮来执行循环，该循环会跳过 i=3 的步进。</p>

<button onclick="myFunction()">点击这里</button>

<p id="demo"></p>

<script>

function myFunction(){

 var x="",i=0;

 for (i=0;i<10;i++){

    if (i==3){

      continue;

     }

  x=x + "该数字为 " + i + "<br>";

   }

 document.getElementById("demo").innerHTML=x;

}

</script>

//用for...in遍历数组内元素

 <p>点击下面的按钮，循环遍历对象 "person" 的属性。</p>

<button onclick="myFunction()">点击这里</button>

<p id="demo"></p>

<script>

function myFunction(){

var x;

var txt="";

var person={fname:"Bill",lname:"Gates",age:56}; 

for (x in person){

txt=txt + person[x];

}

document.getElementById("demo").innerHTML=txt;

}

</script>