坑题

(function(){
     'use strict'
     var a=b=3//这儿由于严格模式，将会出错
 })()
 console.log(a)
 console.log(b)
 //Uncaught ReferenceError: b is not defined,a不会打印

关于严格模式：戳这里

var p=new Promise(function(resolve){
    console.log(1)
    resolve()
}).then(function(){
    console.log(4)
})
console.log(2)
console.log(3)
//1 2 3 4

setTimeout(()=>console.log(4),0)
var p1=new Promise(function(resolve,reject){
    console.log(6)
    setTimeout(()=> console.log(3),0)
    resolve('hello')
}).then(function(val){
    console.log(val)
})
setTimeout(()=> console.log(2),0)
console.log(5)
//6 5 hello 4 3 2

var length = 10
function fn(){
    alert(this.length)
}
var obj = {
    length: 5,
    method: function(fn) {
        fn() // 10
        arguments[0]() // 1
    }
}
obj.method(fn)

function f1(){};
var f2 = function(){};
var f3 = new Function('str','console.log(str)');

var o3 = new f1();
var o1 = {};
var o2 =new Object();

console.log(typeof Object); //function
console.log(typeof Function); //function
console.log(typeof o1); //object
console.log(typeof o2); //object
console.log(typeof o3); //object
console.log(typeof f1); //function
console.log(typeof f2); //function
console.log(typeof f3); //function