JavaScript 中JSON 数据遍历
1. JSON 字符串转对象后遍历
1.1 解析 JSON 字符串
const jsonString = '{"users": [{"id": 1, "name": "张三"}, {"id": 2, "name": "李四"}]}';
const data = JSON.parse(jsonString);// 遍历数组
data.users.forEach(user => {console.log(`ID: ${user.id}, 姓名: ${user.name}`);
});// 1.2 从 API 获取的 JSON
fetch('/api/user/realname/王').then(response => response.json()).then(data => {// 遍历返回的 JSON 数据if (Array.isArray(data)) {data.forEach(user => {console.log(user.realname, user.email);});}});
2. 遍历 JSON 对象（Object）
const user = {"id": 1,"username": "zhangsan","realname": "张三","email": "zhangsan@example.com","department": {"id": 101,"name": "技术部"}
};// 2.1 Object.keys() + forEach
Object.keys(user).forEach(key => {console.log(`${key}: ${user[key]}`);
});// 2.2 for...in 循环（会遍历原型链属性）
for (const key in user) {if (user.hasOwnProperty(key)) {console.log(`${key}: ${user[key]}`);}
}// 2.3 Object.entries() - 获取键值对数组
Object.entries(user).forEach(([key, value]) => {console.log(`${key}: ${JSON.stringify(value)}`);
});// 2.4 Object.values() - 只获取值
Object.values(user).forEach(value => {console.log(value);
});
3. 遍历嵌套的 JSON 数据
const company = {"companyName": "ABC公司","departments": [{"id": 1,"name": "技术部","employees": [{"id": 101, "name": "张三", "role": "前端开发"},{"id": 102, "name": "李四", "role": "后端开发"}]},{"id": 2,"name": "市场部","employees": [{"id": 201, "name": "王五", "role": "市场专员"}]}]
};// 3.1 多层嵌套遍历
company.departments.forEach(dept => {console.log(`部门: ${dept.name}`);dept.employees.forEach(emp => {console.log(` - ${emp.name} (${emp.role})`);});
});// 3.2 递归遍历所有属性
function traverseJSON(obj, depth = 0) {const indent = ' '.repeat(depth);if (Array.isArray(obj)) {obj.forEach(item => traverseJSON(item, depth + 1));} else if (obj !== null && typeof obj === 'object') {Object.entries(obj).forEach(([key, value]) => {if (typeof value === 'object') {console.log(`${indent}${key}:`);traverseJSON(value, depth + 1);} else {console.log(`${indent}${key}: ${value}`);}});} else {console.log(`${indent}${obj}`);}
}traverseJSON(company);
4. 处理从 API 返回的 JSON 数据
// 假设 API 返回：{ "success": true, "data": [{...}, {...}], "total": 2 }async function fetchAndProcessUsers() {try {const response = await fetch('/api/users');const result = await response.json();// 4.1 检查 API 返回状态if (!result.success) {throw new Error(result.message || '请求失败');}// 4.2 遍历数据const users = result.data;// 方式1: 简单遍历users.forEach((user, index) => {console.log(`用户${index + 1}:`, user);});// 方式2: 使用 map 转换数据const userNames = users.map(user => ({id: user.id,displayName: `${user.realname} (${user.username})`,department: user.deptname}));// 方式3: 使用 filter 筛选const activeUsers = users.filter(user => user.status === 'active' && user.deptname === '技术部');// 方式4: 使用 reduce 统计const departmentCount = users.reduce((acc, user) => {acc[user.deptname] = (acc[user.deptname] || 0) + 1;return acc;}, {});console.log('部门统计:', departmentCount);return userNames;} catch (error) {console.error('处理数据失败:', error);}
}
5. 将遍历结果转为 HTML
async function displayUsersInTable() {const response = await fetch('/api/user/realname/王');const users = await response.json();const tableBody = document.querySelector('#userTable tbody');tableBody.innerHTML = ''; // 清空现有内容// 遍历 JSON 数据生成表格行users.forEach(user => {const row = document.createElement('tr');// 创建单元格const cells = [user.id,user.realname,user.username,user.deptname,user.mobile,user.email];cells.forEach(cellData => {const cell = document.createElement('td');cell.textContent = cellData || 'N/A';row.appendChild(cell);});// 添加操作按钮const actionCell = document.createElement('td');actionCell.innerHTML = `<button onclick="editUser(${user.id})">编辑</button><button onclick="deleteUser(${user.id})">删除</button>`;row.appendChild(actionCell);tableBody.appendChild(row);});
}
使用模板字符串
function displayUsersWithTemplate(users) {const container = document.getElementById('userContainer');const userCards = users.map(user => `<div class="user-card"><h3>${escapeHtml(user.realname)}</h3><p><strong>用户名:</strong> ${escapeHtml(user.username)}</p><p><strong>部门:</strong> ${escapeHtml(user.deptname || '未分配')}</p><p><strong>手机:</strong> ${escapeHtml(user.mobile || 'N/A')}</p><p><strong>邮箱:</strong> ${escapeHtml(user.email || 'N/A')}</p><button class="btn-view" data-id="${user.id}">查看详情</button></div>`).join('');container.innerHTML = userCards;// 添加事件监听container.querySelectorAll('.btn-view').forEach(button => {button.addEventListener('click', (e) => {const userId = e.target.dataset.id;viewUserDetail(userId);});});
}
防止 XSS 攻击的简单转义函数
function escapeHtml(text) {const div = document.createElement('div');div.textContent = text;return div.innerHTML;
}
6. 使用现代 JavaScript 特性
6.1 使用可选链和空值合并
users?.forEach(user => {const email = user.email ?? '暂无邮箱';const dept = user.department?.name ?? '未分配部门';console.log(`${user.realname} - ${dept} - ${email}`);
});
6.2 使用解构赋值
users.forEach(({ id, realname: name, email = '无邮箱' }) => {console.log(`ID: ${id}, 姓名: ${name}, 邮箱: ${email}`);
});
6.3 使用 flatMap 处理嵌套数组
const allEmployees = companyData.departments.flatMap(dept => dept.employees.map(emp => ({...emp,department: dept.name}))
);
6.4 使用 Set 去重
const uniqueDepartments = [...new Set(users.map(user => user.deptname))];
