前端学习-JavaScrip学习-js基础03-526互联

循环

案例-九九乘法表

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>

    <style>
        span {
            display: inline-block;
            width: 100px;
            padding: 5px 10px;
            border: 1px solid black;
            margin: 2px;
            text-align: center;
        }
    </style>
</head>
<body>
    <script>
        // let row = +prompt('row:');
        // // let col = +prompt('col:');
        // for(let i = 1;i <= row;i++) {
        //     for(let j = 1;j <= i;j++) {
        //         document.write('⭐');
        //     }
        //     document.write('<br>');
        // }

        for(let i = 1;i <= 9;i++) {
            for(let j = 1;j <= i;j++) {
                document.write(`<span>${i} * ${j} = ${i*j}</span>`);
                // if(j < i) {
                //     document.write(', ');
                // }
            }
            document.write('<br>');
        }
    </script>
</body>
</html>

数组

增删改查

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script>
        let arr = [1,2,3];
        // 增
        arr.push(4,5,6,);
        console.log(arr);
        arr.unshift(-1,0);
        console.log(arr);
        // 筛选数组
        let newArr = [];
        let j = 0;
        for(let i = 0;i < arr.length;i++) {
            if(arr[i] > 2) {
                // newArr[j] = arr[i];
                // j++;
                newArr.push(arr[i]);
            }
        }
        console.log(newArr);
        // 删除数组
        console.log(arr.pop());
        console.log(arr.shift());
        // 从索引号开始全部删除
        arr.splice(2);
        // 从索引号开始删除n个
        arr.splice(2,3);
        console.log(arr);

    </script>
</body>
</html>

案例-柱状图

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>

    <style>
        * {
            margin: 0;
            padding: 0;
        }

        .box {
            display: flex;
            width: 800px;
            height: 300px;
            border-left: 1px solid black;
            border-bottom: 1px solid black;
            margin: 50px auto;
            justify-content: space-around;
            align-items: flex-end;
            text-align: center;
        }

        .box>div {
            display: flex;
            width: 50px;
            background-color: red;
            flex-direction: column;
            justify-content: space-between;
        }

        .box div span {
            margin-top: -20px;
        }

        .box div h4 {
            margin-bottom: -20px;
        }
    </style>
</head>
<body>
    
        <!-- <div style="height: 200px;">
            <span>200</span>
            <h4>season</h4>
        </div>
        <div style="height: 200px;">
            <span>200</span>
            <h4>season</h4>
        </div> -->
    
    <script>
        document.write('<div class="box">');
        let height = [];
        for(let i = 1;i < 5;i++) {
            height.push(prompt(`number ${i} :`));
            document.write(`
            <div style="height: ${height[i - 1]}px;">
                <span>${height[i - 1]}</span>
                <h4>season${i}</h4>
            </div>`) 
        }
        document.write('</div>');
    </script>
</body>
</html>

冒泡排序

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script>
        let arr = [2,4,5,6,22,9,10,111,2,1,32];

        for(let i = 0;i < arr.length - 1;i++) {
            for(let j = 0;j < arr.length - i - 1;j++) {
                let tmp = 0;
                if(arr[j] > arr[j + 1]) {
                    tmp = arr[j];
                    arr[j] = arr[j + 1];
                    arr[j + 1] = tmp;
                }
            }
        }

        console.log(arr);
    </script>
</body>
</html>