Several empty micro-channel applet determines finishing

1.null

var a=null
if(a===null){
	console.log("为空")
}

2.undefined

var a=undefined
if(a==='undefined'){
	console.log("为undefined")
}

3. Null Object

var a={}
if(Object.keys(a).length===0){
	console.log("为{}")
}