for循环是将计数器在for条件中声明。while do循环是将计数器放到while循环之外声明。

While循环

示

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var i=0
 
while(i<10){
    println(i);
    i++;
}
 
function println(a) {
    document.write(a + '<br>');
}

示例说明

 

打印数字9-0

 1 <!DOCTYPE html>
 2 <html lang="en">
 3 <head>
 4 <meta charset="UTF-8">
 5 <title>while循环</title>
 6 </head>
 7 <body>
 8 <script>
 9 var i=9;
10 while(i>=0){
11 print(i);
12 i--;
13 }
14 
15 function print(a){
16     document.write(a+'<br>');
17 }
18 
19 </script>
20 </body>
21 </html>