Summary of js methods for judging whether an object is an empty object

During the interview or development process, we often encounter such a question-how to judge whether an object is an empty object? Let us sum it up together!

Method 1: JSON.stringify() method

• Principle: convert the object into a string, and then judge whether it is equal to "{}"

let obj = {
    
    };
console.log(JSON.stringify(obj) === "{}");  // true

Method 2: for in method

var obj = {
    
    };
var fn = function () {
    
    
  for (var key in obj) {
    
    
    return false;  // 若不为空，可遍历，返回false
  }
  return true;
};
console.log(fn()); // true

Method 3: Object.keys() method

• Principle: Object.keys() method returns an array of object property names. If the length is 0, it is an empty object (ES6 writing method)

let obj = {
    
    };
let arr = Object.keys(obj);
console.log(arr.length == 0); // true

Method 4: Object.getOwnPropertyNames() method

• Principle: The Object.getOwnPropertyNames() method obtains the property names of the object and stores them in an array. If the length is 0, it is an empty object.

var obj = {
    
    };
var arr = Object.getOwnPropertyNames(obj);
console.log(arr.length == 0); // true

Method 5: jQuery's isEmptyObject() method

• Principle: Use the for in method to judge (note: remember to quote jquery when using this method).

var obj = {
    
    };
var b = $.isEmptyObject(obj);
console.log(b); //  true