JS judge whether the object is empty

1、es6 Can be used in Object.keys(obj)

var obj= {};
var arr = Object.keys(obj);
alert(arr.length == 0); //true  It's empty , false  Not empty 

2、 take json Object to json character string , Then judge whether the string is "{}"

var obj= {};
var b = (JSON.stringify(obj) == "{}");
alert(b);   //true  It's empty , false  Not empty