对象的迭代

const obj = {
  name: 'tom',
  age: 18,
  job: 'student'
}

for (let key in obj) {
  console.log(key, obj[key])
}
/* 
name tom
age 18
job student
*/
console.log(Object.keys(obj)) // [ 'name', 'age', 'job' ]
console.log(Object.values(obj)) // [ 'tom', 18, 'student' ]
console.log(Object.entries(obj)) // [ [ 'name', 'tom' ], [ 'age', 18 ], [ 'job', 'student' ] ]