同步更新到本人的语雀，格局更容易看。能够移步:
https://www.yuque.com/diracke...
指标:
1、看try...catch... 与 .then().catch() 的catch有什么不同。
2、在promise中throw err是否被两种catch捕捉到。
先贴用到的代码
会有handle1, handle2, handle3, handle4对应四种不同的状况
运行后果和论断都写在各行代码之后了。
先写论断:
1、 .then.catch中catch的优先级高于try...catch...中的catch;
2、 在promise中throw会将promise实例变为rejected状态;
3、 异步的状况下，try...catch...中的catch无奈解决rejected状态的promise.
async function axiosLike(isSuccess, info = {}) {
return new Promise((resolve, reject) => {
if (isSuccess) { if (info.code === "0") { resolve(info.data); } else { reject(info.msg); }} else { throw "serve err";}});
}
const tempInfoSuccess = {
code: "0",
data: { name: "mike", age: 15 },
msg: "success",
};
const tempInfoFailed = {
code: "2",
data: { name: "mike", age: 15 },
msg: "unknow exception",
};
async function handle1(isSuccess, info = {}) {
try {
const res = await axiosLike(isSuccess, info);console.log("res->", res);} catch (err) {
console.log("err->", err);}
}
// handle1(true, tempInfoSuccess); // res-> { name: "mike", age: 15 }
// handle1(true, tempInfoFailed); // err-> unknow exception
// handle1(false); // err-> serve err
// try...catch 的catch会捕捉 reject()的状态,且可能拿到reject(err)中的err
// try...catch 的catch也会捕捉 throw抛出的异样 并且也能拿到 throw err 的 err
function handle2(isSuccess, info = {}) {
axiosLike(isSuccess, info)
.then((res) => { console.log("res->", res);}).catch((err) => { console.log("err->", err);});}
// handle2(true, tempInfoSuccess); // res-> { name: "mike", age: 15 }
// handle2(true, tempInfoFailed); // err-> unknow exception
// handle2(false); // err-> serve err
// Promise.then().catch() 中的catch会捕捉 reject()的状态,且可能拿到reject(err)中的err
// Promise.then().catch() 中的catch也会捕捉 throw抛出的异样 并且也能拿到 throw err 的 err
function handle3(isSuccess, info = {}) {
try {
axiosLike(isSuccess, info) .then((res) => { console.log("res->", res); }) .catch((err) => { console.log("err in .then.catch ->", err); });} catch (err) {
console.log("err in try...catch ->", err);}
}
// handle3(true, tempInfoFailed); // err in .then.catch -> unknow exception
// handle3(false); // err in .then.catch -> serve err
//
function handle4(isSuccess, info = {}) {
try {
axiosLike(isSuccess, info).then((res) => { console.log("res->", res);});} catch (err) {
console.log("err in try...catch ->", err);}
}
// handle4(true, tempInfoFailed); // 报错如下 ↓
/*
UnhandledPromiseRejectionWarning: unknow exception
UnhandledPromiseRejectionWarning: Unhandled promise rejection.
This error originated either by throwing inside of an async function without a catch block,
or by rejecting a promise which was not handled with .catch().
*/
// try...catch 的catch不能解决rejected状态的promise.
handle4(false); // 报错如下 ↓
/*
UnhandledPromiseRejectionWarning: serve err
UnhandledPromiseRejectionWarning: Unhandled promise rejection.
This error originated either by throwing inside of an async function without a catch block,
or by rejecting a promise which was not handled with .catch().
*/
// throw err 也将promise实例变为了rejected状态,而try...catch 的catch不能解决
// 察看handle4()的两条执行后果,能够发现,异步后果中的报错,try...catch中的catch是无奈解决的。