javascript基础非常

已经快被开除的小前端

于 2019-07-30 15:08:22 发布

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CC 4.0 BY-SA版权

本文链接：https://blog.youkuaiyun.com/weixin_42880952/article/details/97781298

本文通过多个示例深入探讨了JavaScript中的变量作用域、函数执行上下文及执行流程，包括变量提升、函数调用堆栈、异步执行顺序等关键概念。

var a = 10;
function foo(){
	console.log(a)
	var a = 20;
	console.log(a);
}
foo()  //undefined  //20


function foo(){
	var a = 20;
}
foo()  
console.log(a) 
//报错 a   is   undefined

var a = 10;
function foo(){
	console.log(a)
	var b = 20;
}
foo()  //undefined

var a = 1;
function aaa(a){console.log(a)}
aaa(a+'1'),
console.log(a); //11  1

function Hello() {
   alert("Hello");
}

Hello();  //Hello World

function Hello() {
   alert("Hello World");
}

Hello();  //Hello World

console.log('111');

setTimeout(function(){
    console.log('222');
},1000);

console.log('333');

setTimeout(function(){
    console.log('444');
},1000);

console.log('555');

//111 //333 //555  //222 //444

javascript基础 非常

javascript基础非常