我想结合使用我需要等待的异步功能和不需要等待的功能。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,是否触发catch函数?在第二个函数doSecondAsynchronousStuffIDoNotNeedToAwait()
中,有没有更好的方法来处理结果?该代码是否有缺点,或者可以编写更好的方法?
我希望问题很清楚,代码也足够简单易懂。如果没有,请发表评论,我将编辑我的问题。谢谢:)
答案 0 :(得分:1)
好吧,让我们尝试一下:
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();
通过运行代码段可以看到,try / catch不会捕获错误,但是您会得到全局错误?由于Promise错误不在try catch的“范围”内,因此,异步await try / catch捕获的唯一错误是当抛出正常异常或等待的Promise被拒绝时。因此,您必须使用catch函数以老式方式处理异步错误。
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();
答案 1 :(得分:1)
测试起来很简单:
await
值可按预期工作:
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()
在没有await
的情况下,您会收到未捕获的承诺拒绝错误(我认为只有在控制台中才能看到该错误):
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
,该函数不会等待承诺被解决,并且该函数会在有机会捕获被拒绝的承诺之前完成。