JavaScript: setTimeout & setInterval
let i = 0 setTimeout(function (n) { console.log(55, n) }, 1000, setTimeout(function () { console.log(44, i) i++ return i+2 }))
先计算第三参数, 返回值为Timeout对象, 传递给第一参数, 浏览器中返回window
const obj = { a: function () { console.log(this) setTimeout(function () { console.log(this) }, 1000) } } // obj.a() let b = obj.a b()
Node:
Browser:
Node中指向Timeout对象, Browser中指向全局window
const obj = { a: function () { console.log(this) setTimeout(function () { console.log(this) }, 1000) } } obj.a()
Node:
Browser:
Arrow Function
const obj = { a: function () { console.log(this) setTimeout(() => { console.log(this) }, 1000) } } obj.a()
一致
const obj = { a: function () { console.log(this) setTimeout(() => { console.log(this) }, 1000) } } let b = obj.a b()
Node
Browser
当b执行时, this才确定, setTimeout的arrow function绑定刚确定的this