JavaScript中思考do...while 和 while语句的区别

Do...while和while...do的区别在于对于临界值的测试上。当在执行的时候只选择临界值来测试时，你会发现do...while至少要执行一次，而while...do则一次都不会执行。但是，当不去考虑临界值的时候，do...while和while...do的执行结果是一样的。让我们用事实来说话吧：

只测试临界值：

 1 <!DOCTYPE html>
 2 <html>
 3 <body>
 4 <p>Try to practice while statement!</p>
 5 <p id = "demo"></p>
 6 <script>
 7     var x = "";
 8     var i = 0;
 9     var x = "";
10     var i = 0;
11     while(i < 0)
12     {
13         x += "The number is " + i + "." + "<br>";
14         i ++;
15         document.getElementById("demo").innerHTML = x;
16     }
17     
18     do
19     {
20         x +="The number is " + i + "." + "<br>";
21         i++;
22         document.getElementById("demo").innerHTML = x;
23     }
24     while(i < 0); 
25 </script>
26 </body>
27 </html>

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