1，判断对象是否存在-------!$.isEmptyObject()

if(!$.isEmptyObject(obj)){
	console.log('exit obj')
}else{
	console.log('no exit obj')
}

2，判断对象属性是否为空-----Object.keys().length

if(Object.keys(obj).length!=0){
	console.log('obj not null')
}else{
	console.log('obj is null')
}

3，判断对象属性是否存在------hasOwnProperty

if(obj.hasOwnProperty('name')){
	console.log('exit property')
}else{
	console.log('no exit property')
}

4，判断对象是否为空对象

4.1，将json对象转化为json字符串，再判断该字符串是否为"{}"

var data = {};
var b = (JSON.stringify(data) == "{}");
alert(b); //true

4.2，for in 循坏判断

var obj = {};
var b = funciton(){
	for (var key in obj){
		return false;
	}
	return true;
}
alert(b); //true

4.3，ES6的Object.keys()：返回值是对象种属性名组成数组

var data ={};
var arr = Object.keys(data);
alert(arr.length==0);//true