JS monitors empty objects and empty references

1. An empty object ： Represents an object , It does not contain any properties and methods
2. Null reference ： Point to null

Example ： Both methods can create an empty object , One is the constructor method , And one is object literal representation

    let obj = new Object()
    let obj1 = {
    }

1. You can't use null To monitor whether it is an empty object , An empty object does not equal null

2. Use JSON.stringify==’{}' To detect whether the object is empty , Not recommended

3. utilize object.keys(obj) Get an array of attributes , If the array length is 0, Description is empty object
   

4. obtain obj All attributes of （ Excluding the prototype chain ）, It is very similar to the previous method