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我有 json 信息（如下所示）。我可以轻松打印教室名称和级别。但我不知道如何循环遍历学生以将其打印出来。我不确定如何在 foreach 循环中执行 foreach 循环。我的 HTML 不是一成不变的，如果需要，可以稍作更改。

<div id="results">
    <div class="classroom">
        <div class="cr-name">Name: maths class</div>
        <div class="cr-level">Level: 4</div>
        <div class="students">
            <div class="student">john 19</div>
            <div class="student">Mike 34</div>
            <div class="student">Billy 19</div>
        </div>
    </div><br>
    <div class="classroom">
        <div class="cr-name">Name: English class</div>
        <div class="cr-level">Level: 2</div>
        <div class="students">
            <div class="student">Sam 24</div>
            <div class="student">Timmy 32</div>
            <div class="student">John 19</div>
            <div class="student">Paul 54</div>
        </div>
    </div>
</div><br>

json 数据如下所示：

[
  {
    "classroom": "maths class",
    "students": [
      {
        "name": "john",
        "age": 20
      },
      {
        "name": "Mike",
        "age": 34
      },
      {
        "name": "Billy",
        "age": 19
      }
    ],
    "level": 4
  },
  {
    "classroom": "English class",
    "students": [
      {
        "name": "Sam",
        "age": 24
      },
      {
        "name": "Timmy",
        "age": 32
      },
      {
        "name": "John",
        "age": 19
      },
      {
        "name": "Paul",
        "age": 54
      }
    ],
    "level": 2
  }
]

我的 HTML：

<div id="results">
</div>

我的Javascript（其中数据是上面的json信息）：

if(typeof data !== 'undefined' && data.length > 0) {
    data.forEach((myclass, idx) => {
        $("#results").append(`
        <div class="classroom">
            <div class="cr-name">Name: ${data.classroom}</div>
            <div class="cr-level">Level: ${data.level}</div>
        </div><br>
      `);
    });
}

解决方案

将学生数组和.map每个项目转换为 HTML 字符串，例如<div class="student">john 19</div>，然后将其连接在一起：

const data = [
  {
    "classroom": "maths class",
    "students": [
      {
        "name": "john",
        "age": 20
      },
      {
        "name": "Mike",
        "age": 34
      },
      {
        "name": "Billy",
        "age": 19
      }
    ],
    "level": 4
  },
  {
    "classroom": "English class",
    "students": [
      {
        "name": "Sam",
        "age": 24
      },
      {
        "name": "Timmy",
        "age": 32
      },
      {
        "name": "John",
        "age": 19
      },
      {
        "name": "Paul",
        "age": 54
      }
    ],
    "level": 2
  }
]

data.forEach(({ classroom, level, students }) => {
    $("#results").append(`
    <div class="classroom">
        <div class="cr-name">Name: ${classroom}</div>
        <div class="cr-level">Level: ${level}</div>
        <div class="students">
            ${
              students
                .map(({ name, age }) => `<div class="student">${name} ${age}</div>`)
                .join('')
            }
        </div>
    </div><br>
  `);
});

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<div id="results"></div>

那就是输入数据是否可信。如果它不可信，直接编写这样的 HTML 字符串可能会导致任意代码执行。如果这是您需要防止的事情，请确保先删除所有<>括号：

name.replace(/[<>]/g, '')

age.replace(/[<>]/g, '')