js的流程控制分支

一时失言乱红尘 2022-09-09 04:58 227阅读 0赞

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<!DOCTYPE html>
    <html lang="en">
    <head>
        <meta charset="UTF-8">
        <meta http-equiv="X-UA-Compatible" content="IE=edge">
        <meta name="viewport" content="width=device-width, initial-scale=1.0">
        <title>Document</title>
        <script>
            var year=parseInt(prompt("请输入年份"));
            console.log(typeof year);
            if((year%4==0 && year %4 !=0)|| year%400==0){
                alert(year+'是闰年');
            }else {
                alert(year+'是平年');
            }
        </script>
    </head>
    <body>
        
    </body>
    </html>

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![在这里插入图片描述][a43b911d3ceb4534ab7d6bb25ed2ae97.png]

<!DOCTYPE html>
    <html lang="en">
    <head>
        <meta charset="UTF-8">
        <meta http-equiv="X-UA-Compatible" content="IE=edge">
        <meta name="viewport" content="width=device-width, initial-scale=1.0">
        <title>Document</title>
        <script>
            var score=prompt("请输入分数");
            if (score>=90){
                // console.log(score);
                // console.log(typeof score);
                alert('A')
            } else if(80<=score<=90){
                alert('B')
            }else if(70<=score<=80){
                alert('C')
            }else if(60<=score<=70){
                alert('D')
            }else {
                alert('E')
            }
        </script>
    </head>
    <body>
        
    </body>
    </html>

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如果从小到大，你写一个90的，前面>60的也会输出

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三元表达式理解为3个表达式。

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<!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>

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