同步回調(diào)函數(shù)
按照正常順序執(zhí)行
const arr = [1, 2, 3]
arr.forEach(item => {
console.log(item)
})
console.log('forEach 之后')
輸出為:
1
2
3
forEach 之后
異步回調(diào)函數(shù)
setTimeout將回調(diào)函數(shù)放在下一個(gè)任務(wù)隊(duì)列執(zhí)行
setTimeout(()=>{
console.log('timeout callback')
},0)
console.log('timeout end')
輸出為
timeout end
timeout callback
