我有一个fetch-api POST请求:
fetch(url, {
method: 'POST',
body: formData,
credentials: 'include'
})
我想知道这个的默认超时时间是多少?我们如何将它设置为特定的值，比如3秒或不定秒?
当前回答
正确的错误处理技巧
正常的做法:
为了在大多数情况下增加超时支持，建议引入一个Promise实用函数，如下所示:
function fetchWithTimeout(resource, { signal, timeout, ...options } = {}) {
const controller = new AbortController();
if (signal != null) signal.addEventListener("abort", controller.abort);
const id = timeout != null ? setTimeout(controller.abort, timeout) : undefined;
return fetch(resource, {
...options,
signal: controller.signal
}).finally(() => {
if (id != null) clearTimeout(id);
});
}
调用控制器。abort或拒绝setTimeout回调函数中的承诺会扭曲堆栈跟踪。
这是次优的，因为如果需要对错误后日志进行分析，就必须在调用fetch方法的函数中添加带有日志消息的样板错误处理程序。
好专业知识:
为了保留错误及其堆栈跟踪，可以应用以下技术:
function sleep(ms = 0, signal) { return new Promise((resolve, reject) => { const id = setTimeout(() => resolve(), ms); signal?.addEventListener("abort", () => { clearTimeout(id); reject(); }); }); } async function fetch( resource, options ) { const { timeout, signal, ...ropts } = options ?? {}; const controller = new AbortController(); let sleepController; try { signal?.addEventListener("abort", () => controller.abort()); const request = nodeFetch(resource, { ...ropts, signal: controller.signal, }); if (timeout != null) { sleepController = new AbortController(); const aborter = sleep(timeout, sleepController.signal); const race = await Promise.race([aborter, request]); if (race == null) controller.abort(); } return request; } finally { sleepController?.abort(); } } (async () => { try { await fetchWithTimeout(new URL(window.location.href), { timeout: 5 }); } catch (error) { console.error("Error in test", error); } })();
其他回答
正确的错误处理技巧
正常的做法:
为了在大多数情况下增加超时支持，建议引入一个Promise实用函数，如下所示:
function fetchWithTimeout(resource, { signal, timeout, ...options } = {}) {
const controller = new AbortController();
if (signal != null) signal.addEventListener("abort", controller.abort);
const id = timeout != null ? setTimeout(controller.abort, timeout) : undefined;
return fetch(resource, {
...options,
signal: controller.signal
}).finally(() => {
if (id != null) clearTimeout(id);
});
}
调用控制器。abort或拒绝setTimeout回调函数中的承诺会扭曲堆栈跟踪。
这是次优的，因为如果需要对错误后日志进行分析，就必须在调用fetch方法的函数中添加带有日志消息的样板错误处理程序。
好专业知识:
为了保留错误及其堆栈跟踪，可以应用以下技术:
function sleep(ms = 0, signal) { return new Promise((resolve, reject) => { const id = setTimeout(() => resolve(), ms); signal?.addEventListener("abort", () => { clearTimeout(id); reject(); }); }); } async function fetch( resource, options ) { const { timeout, signal, ...ropts } = options ?? {}; const controller = new AbortController(); let sleepController; try { signal?.addEventListener("abort", () => controller.abort()); const request = nodeFetch(resource, { ...ropts, signal: controller.signal, }); if (timeout != null) { sleepController = new AbortController(); const aborter = sleep(timeout, sleepController.signal); const race = await Promise.race([aborter, request]); if (race == null) controller.abort(); } return request; } finally { sleepController?.abort(); } } (async () => { try { await fetchWithTimeout(new URL(window.location.href), { timeout: 5 }); } catch (error) { console.error("Error in test", error); } })();
编辑1
正如注释中所指出的，原始答案中的代码即使在承诺被解析/拒绝之后也会继续运行计时器。
下面的代码修复了这个问题。
function timeout(ms, promise) {
return new Promise((resolve, reject) => {
const timer = setTimeout(() => {
reject(new Error('TIMEOUT'))
}, ms)
promise
.then(value => {
clearTimeout(timer)
resolve(value)
})
.catch(reason => {
clearTimeout(timer)
reject(reason)
})
})
}
原来的答案
它没有指定的默认值;该规范根本没有讨论超时。
你可以为promise实现自己的超时包装器:
// Rough implementation. Untested.
function timeout(ms, promise) {
return new Promise(function(resolve, reject) {
setTimeout(function() {
reject(new Error("timeout"))
}, ms)
promise.then(resolve, reject)
})
}
timeout(1000, fetch('/hello')).then(function(response) {
// process response
}).catch(function(error) {
// might be a timeout error
})
如https://github.com/github/fetch/issues/175所述 评论来源:https://github.com/mislav
fetchTimeout (url,options,timeout=3000) {
return new Promise( (resolve, reject) => {
fetch(url, options)
.then(resolve,reject)
setTimeout(reject,timeout);
})
}
在取回API中还没有超时支持。但这可以通过一个承诺来实现。
如。
function fetchWrapper(url, options, timeout) {
return new Promise((resolve, reject) => {
fetch(url, options).then(resolve, reject);
if (timeout) {
const e = new Error("Connection timed out");
setTimeout(reject, timeout, e);
}
});
}
使用c-promise2库，可取消的获取超时可能像这样(Live jsfiddle演示):
import CPromise from "c-promise2"; // npm package
function fetchWithTimeout(url, {timeout, ...fetchOptions}= {}) {
return new CPromise((resolve, reject, {signal}) => {
fetch(url, {...fetchOptions, signal}).then(resolve, reject)
}, timeout)
}
const chain = fetchWithTimeout("https://run.mocky.io/v3/753aa609-65ae-4109-8f83-9cfe365290f0?mocky-delay=10s", {timeout: 5000})
.then(request=> console.log('done'));
// chain.cancel(); - to abort the request before the timeout
这段代码作为一个npm包cp-fetch
