我想将需要等待的异步函数和不需要等待的函数结合起来。首先是代码。。。
async function doSomeStuff() {
try {
const data = await getDataFromDatabase()
if(data.canDoStuff == "yes") {
doAsynchronousStuffIDoNotNeedToAwait()
}
if(data.canDoSecondStuff == "yes") {
doSecondAsynchronousStuffIDoNotNeedToAwait()
.then(result => console.log("Done!");
}
} catch(err) {
console.log(err)
}
}
这是我的问题。如果我的doAsynchronousStuffIDoNotNeedToAwait()
抛出错误,它会触发catch函数吗?在第二个函数doSecondAsynchronousStuffIDoNotNeedToAwait()
中,是否有更好的方法来处理结果?这段代码是否有一些缺点,或者可以用更好的方式编写?
我希望问题清楚,代码简单易懂。如果没有,请留下评论,我将编辑我的问题。谢谢:(
好吧,让我们试一试:
function getDataFromDatabase() {
return new Promise((resolve) => {
setTimeout(resolve, 250, {canDoStuff: 'yes', canDoSecondStuff: 'yes'});
});
}
function doAsynchronousStuffIDoNotNeedToAwait() {
return new Promise((resolve) => {
setTimeout(resolve, 250);
});
}
function doSecondAsynchronousStuffIDoNotNeedToAwait() {
return new Promise((_, reject) => {
setTimeout(reject, 250, 'error: doSecondAsynchronousStuffIDoNotNeedToAwait()');
});
}
async function doSomeStuff() {
try {
const data = await getDataFromDatabase()
if(data.canDoStuff == "yes") {
doAsynchronousStuffIDoNotNeedToAwait()
}
if(data.canDoSecondStuff == "yes") {
doSecondAsynchronousStuffIDoNotNeedToAwait()
.then(result => console.log("Done!"));
}
} catch(err) {
console.log(err)
}
}
doSomeStuff();
正如您通过运行代码片段所看到的,不,try/catch不会捕捉到错误,但您将获得全局?错误由于promise不在try-catch的"范围"内,异步等待try/catch捕获的唯一错误是抛出正常异常或等待的promise被拒绝。因此,您必须使用catch函数以旧的方式处理异步错误。
function getDataFromDatabase() {
return new Promise((resolve) => {
setTimeout(resolve, 250, {canDoStuff: 'yes', canDoSecondStuff: 'yes'});
});
}
function doAsynchronousStuffIDoNotNeedToAwait() {
return new Promise((resolve) => {
setTimeout(resolve, 250);
});
}
function doSecondAsynchronousStuffIDoNotNeedToAwait() {
return new Promise((_, reject) => {
setTimeout(reject, 250, 'error: doSecondAsynchronousStuffIDoNotNeedToAwait()');
});
}
async function doSomeStuff() {
try {
const data = await getDataFromDatabase()
if(data.canDoStuff == "yes") {
doAsynchronousStuffIDoNotNeedToAwait()
}
if(data.canDoSecondStuff == "yes") {
doSecondAsynchronousStuffIDoNotNeedToAwait()
.then(result => console.log("Done!")).catch((err) => console.log(err));
}
} catch(err) {
console.log(err)
}
}
doSomeStuff();
测试起来很简单:
await
使值按预期工作:
function getDataFromDatabase(){
return Promise.resolve({canDoStuff: "yes"})
}
function doAsynchronousStuffIDoNotNeedToAwait(){
return Promise.reject("whoops")
}
async function doSomeStuff() {
try {
const data = await getDataFromDatabase()
if(data.canDoStuff == "yes") {
let d = await doAsynchronousStuffIDoNotNeedToAwait()
}
} catch(err) {
console.log("caught error:", err)
}
}
doSomeStuff()
如果没有await
,你会得到一个未捕获的承诺拒绝错误(我认为只有在控制台中才能在SO上看到(:
function getDataFromDatabase(){
return Promise.resolve({canDoStuff: "yes"})
}
function doAsynchronousStuffIDoNotNeedToAwait(){
return Promise.reject("whoops")
}
async function doSomeStuff() {
try {
const data = await getDataFromDatabase()
if(data.canDoStuff == "yes") {
doAsynchronousStuffIDoNotNeedToAwait()
}
} catch(err) {
console.log("caught error", err)
}
}
doSomeStuff()
这是有道理的,因为如果没有await
,函数不会等待promise解析,并且函数在有机会捕获被拒绝的promise之前完成。