JavaScript——Five methods for object judgment

For example: when we make a shopping cart in an e-commerce project, when there are products in the shopping cart, it is a page, but when we empty the shopping cart, the page displays another page, for example: shopping is an empty page. At this point, we need to judge whether the object of commodity is empty.

For example: when judging whether an object is empty, it is not allowed to directly use obj == {}.

The following are 5 common ways to judge whether an object is empty:

1.  JSON.stringify converts the object into a string form, and then judges whether it is equal to '{}'

let obj = {};
  console.log(JSON.stringify(obj) == '{}');

 

      2. Use the object.keys() method in ES6 to return an array containing all property names of the object, and then check whether the length of the array is 0.

 

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

  3. Use the for in loop to traverse the property names of the object. Returns false if not empty, true if empty

 var obj = {};
  var aaa= function(obj){
    for(let key in obj){
      return false;
    }
    return true;
  }
  console.log(aaa(obj));

  4. Use Object.getOwnPropertyNames() to get the object property name, save it in the array, and then judge whether the length of the array is 0

  var obj = {};
  console.log(Object.getOwnPropertyNames(obj) == 0); 

 

  5.5. Use the isEmptyObject method in jq

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