A simple way to determine whether an object {} is an empty object in JavaScript

I encountered a problem when working on a project, to determine whether an object is an empty object. I found that it can be judged this way, and the code is:

1. Code 1:

var a = {};
if(!a){ console.log(1);}
else if(a == null) { console.log(2);}
else { console.log(3);}

The result is: 3

2. Code 2:

var b = {};
if(b == {}){ console.log(4);}
if(b == '{}') { console.log(5);}
if(typeof(b) == 'object') { console.log(6);}

The result is: 6

3. Code 3:

var c = {};
if(JSON.stringify(c) == "{}"){ console.log(7);}

var c = {};
if(JSON.stringify(c) == "{}"){ console.log(7);}

The result is: 7

So you can use the method of code 3 to determine whether the object is an empty object{};

If the object is not empty, and you know that when the object is not empty, a certain attribute (such as {id:111}) must exist, you can judge like this:

4. Code 4:

var d = {};
var e = {id:111};
if(d.id){ console.log(8);}
if(e.id){ console.log(9);}

The result is: 9

Summary: Obviously the judgment method of code 3 is relatively "strong", but the efficiency is obviously not as good as the judgment method of code 4

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