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              <div id="result1"></div>
<div id="result2"></div>
            
          
!
            
              let school = {
    name: 'Hope middle school',
    created: '2001',
    classes: [
        {
            name: '三年二班',
            teachers: [
                { name: '张二蛋', age: 26, sex: '男', actor: '班主任' },
                { name: '王小妞', age: 23, sex: '女', actor: '英语老师' }
            ]
        },
        {
            name: '明星班',
            teachers: [
                { name: '欧阳娜娜', age: 29, sex: '女', actor: '班主任' },
                { name: '李易峰', age: 28, sex: '男', actor: '体育老师' },
                { name: '杨幂', age: 111, sex: '女', actor: '艺术老师' }
            ]
        }
    ]
};

// 常规做法
const result1 = 
school.classes &&
school.classes[0] &&
school.classes[0].teachers &&
school.classes[0].teachers[0] &&
school.classes[0].teachers[0].name

// reduce方法
const get = (p, o) => p.reduce((xs, x) => (xs && xs[x] ? xs[x] : null), o);
const result2 = get(['classes', 0, 'teachers', 0, 'name'], school);   // 张二蛋

document.querySelector("#result1").textContent = result1;
document.querySelector("#result2").textContent = result2;
            
          
!
999px
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