Detailed explanation of native JS asynchronous and single-threaded
What is asynchronous (versus synchronous)? This article mainly shares with you the detailed explanation of native JS asynchronous and single-threaded. I hope it can help everyone.
//异步
console.log(100);
setTimeout(function(){
console.log(200);
},1000);
console.log(300);
//同步
console.log(100);
alert(200);
console.log(300);//同步会阻塞等待When is asynchronous required?
--When waiting may occur
--During the waiting process, the execution of the program cannot be blocked like alert
--So all "waiting situations" require asynchronous
Scenarios where the front-end uses asynchronous
Scheduled tasks:
setTimeout/setInterval
console.log(100);
setTimeout(function(){
console.log(200)
},1000);
console.log(300);
//同步
console.log(100);
alert(200);
console.log(300);
网络请求：ajax请求，动态<img>加载
//ajax
console.log('start');
$.get('xxx',function(){
console.log(data);
})
console.log('end');//startenddata
//img
console.log('start');
var img = document.creatElement('img');
img.onload = function(){
console.log(loaded);
}
img.src = 'xxxxxxxxxxxxxxxx';
console.log('end')//startendloaded
事件绑定
console.log('start');
var btn1 = document.getElementById('btn1');
btn1.addEventListener('click',function(){
console.log('clicked');
})
console.log('end')
异步和单线程
同步和异步的区别？分别举一个同步和异步的例子
同步会阻塞代码执行，而异步不会
alert是同步，setTimeout是异步
一个关于setTimeout的笔试题
console.log(1);
setTimeout(function(){
console.log(2)
},0);
console.log(3);
setTimeout(function(){
console.log(4);
},1000);
console.log(5);
//13524What are the scenarios where the front-end uses asynchronous
Scheduled tasks: setTimeout, setInterval
ajax request, img loading
Event binding
Related recommendations:
Example detailed js Asynchronous programming
Several JavaScript asynchronous loading related issues
Detailed explanation of single-threaded JS execution issues
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