var obj;
obj == null //true
obj === undefined //true
//判断对象是不是空{}
function isEmpty(obj){
for(let key in obj){
if(obj.hasOwnProperty(key)){
return false
}
}
return true
}
var obj={}
console.log(isEmpty(obj)) //true
let arr=[]
arr instanceof Array && arr.length ===0 //true
typeof 一般判断基本js类型 (typeof [] typeof {} typeof null都是object) instanceof 判断引用类型 typeof 结果值共有:"string" "object" "undefined" "boolean" "number" "function"
//判断是Array还是Object
function isArrayObj(obj){
if(obj instanceof Array){
return 'Array'
}else if(obj instanceof Object){
return 'Object'
}else{
return 'other'
}
}
Array.prototype.min=function(){
let minNum=this[0]
for(let a of this){
if(a<minNum){
minNum=a
}
}
return minNum
}
console.log(arr.min())
JavaScript 日期处理类库 http://momentjs.cn/
低版本浏览器补丁类库:https://polyfill.io/v3/