AB 序列完成

async function A() {return new Promise<void>((resolve,reject)=>{setTimeout(()=>{console.log('A ok');resolve()},1000)})
}async function B() {return new Promise<void>((resolve,reject)=>{setTimeout(()=>{console.log('B ok');resolve()},1000)})
}async function main(){console.log('task start');await A()await B()console.log('task end');
}main()

AB 同时进行

async function A() {return new Promise<void>((resolve,reject)=>{setTimeout(()=>{console.log('A ok');resolve()},1000)})
}async function B() {return new Promise<void>((resolve,reject)=>{setTimeout(()=>{console.log('B ok');resolve()},2000)})
}async function main(){console.log('task start');Promise.all([A(),B()]).then(()=>{console.log('task end');})
}
main()