判断对象是否是个空对象

1. 遍历，根据是否有值

for...in...

2. 整个对象转换为数组

Object.entries

3. 转为JSON字符串

JSON.stringify()

4. 获取对象的属性名并以数组形式返回

Object.getOwnPropertyNames() / Object.keys()

---

// for...in...
let obj = {}
let isEmpty = true;
for(var i in obj) {
   isEmpty = false
}
console.log(isEmpty)

// key的遍历 ： Object.getOwnPropertyNames
let obj = {}
console.log(Object.getOwnPropertyNames(obj))

// key的遍历： Object.keys 获取key的数组
let obj = {}
let isEmpty = Object.keys(obj).length === 0

// 对象转化为数组的遍历： Object.entries
let obj = {}
let isEmpty;
isEmpty = (Object.entries(obj).length === 0) && (typeof obj === 'object')
console.log(isEmpty)

// JSON字符串
let obj = {}
let isEmpty;
isEmpty = JSON.stringify(obj) === '{}'
console.log(isEmpty)