我在理解Promise功能如何工作方面遇到了一些问题，我之前使用过Bluebird但是我想尝试学习新的await / async标准，以便作为程序员进行改进。我已经使用了async / await并在我认为合适的情况下创建了promises，但是函数仍然无序执行。
我在最新版本的Node with Webpack上运行它，我没有收到任何有意义的错误。它运行正常，不如预期。运行时的输出是：
Searching the Web for: Test String
Web search Completed!
Promise { <pending> }
Response Handler Completed!
理想情况下，我希望回复：
Searching the Web for: Test String
Response Handler Completed
Web search Completed
然后返回我的响应处理程序的输出。
有人能发现我的错误吗？
const https = require('https');
// Replace the subscriptionKey string value with your valid subscription key.
const subscriptionKey = '<samplekey>';
const host = 'api.cognitive.microsoft.com';
const path = '/bing/v7.0/search';
const response_handler = async (response) => {
return new Promise((resolve, reject) => {
let body = '';
response.on('data', (d) => {
body += d;
resolve(body);
});
response.on('end', () => {
console.log('\nRelevant Headers:\n');
for (const header in response.headers)
// header keys are lower-cased by Node.js
{
if (header.startsWith('bingapis-') || header.startsWith('x-msedge-')) { console.log(`${header}: ${response.headers[header]}`); }
}
body = JSON.stringify(JSON.parse(body), null, ' ');
//console.log('\nJSON Test Response:\n');
//console.log(body);
});
response.on('error', (e) => {
console.log(`Error: ${e.message}`);
});
console.log('Response Handler Completed!');
});
};
const bing_web_search = async (search) => {
return new Promise((resolve, reject) => {
console.log(`Searching the Web for: ${search}`);
const request_params = {
method: 'GET',
hostname: host,
path: `${path}?q=${encodeURIComponent(search)}&$responseFilter=${encodeURIComponent('Webpages')}&count=${50}`,
headers: {
'Ocp-Apim-Subscription-Key': subscriptionKey,
},
};
const req = https.request(request_params, response_handler);
console.log('Web search Completed!');
console.log(req.body);
req.end();
});
};
module.exports = {
search: async (search) => {
if (subscriptionKey.length === 32) {
const result = await bing_web_search(search);
console.log('Search Completed');
} else {
console.log('Invalid Bing Search API subscription key!');
console.log('Please paste yours into the source code.');
}
},
};
答案 0 :(得分：0)
有点晚了但是下面的内容应该让你在路上，我对代码进行了更改。如果您有任何疑问，请告诉我。
const https = require('https');
// Replace the subscriptionKey string value with your valid subscription key.
const subscriptionKey = '<samplekey>';
const host = 'api.cognitive.microsoft.com';
const path = '/bing/v7.0/search';
const response_handler = (resolve,reject) => (response) => { // no need for async, you return a promise
//this one does not return anything, it's the handler for the response and will resolve
// or reject accordingly
let body = '';
response.on('data', (d) => {
body += d;
//cannot resolve yet, we're not done
// you can resolve on end maybe? I don't know nodejs http
// if end event is called when request fails then end would not
// be the correct way either, better use fetch api
//resolve(body);
});
response.on('end', () => {
console.log('\nRelevant Headers:\n');
for (const header in response.headers)
// header keys are lower-cased by Node.js
{
if (header.startsWith('bingapis-') || header.startsWith('x-msedge-')) { console.log(`${header}: ${response.headers[header]}`); }
}
body = JSON.stringify(JSON.parse(body), null, ' ');
resolve(body);//resolving the promise returned by bing_web_search
//console.log('\nJSON Test Response:\n');
//console.log(body);
});
response.on('error', (e) => {
console.log(`Error: ${e.message}`);
//need to reject with the error
reject(e);
});
console.log('Response Handler Completed!');
};
//no need to specify async, you are not awaiting anything
// you are creating a promise, when using non promise asynchronous
// functions that work with callbacks or event emitting objects
// you need resolve and reject functions so you have to return
// new Promise(
// (resolve,reject)=>somecallbackNeedingFunction((err,result)=>
// err ? reject(err) : resolve(result)
// )
// )
const bing_web_search = (search) => {
return new Promise((resolve, reject) => {
console.log(`Searching the Web for: ${search}`);
const request_params = {
method: 'GET',
hostname: host,
path: `${path}?q=${encodeURIComponent(search)}&$responseFilter=${encodeURIComponent('Webpages')}&count=${50}`,
headers: {
'Ocp-Apim-Subscription-Key': subscriptionKey,
},
};
const req = https.request(
request_params,
response_handler(resolve,reject)//passing this resolve and reject
);
//no, request not completed, we just started
console.log('Web search Completed!');
// console.log(req.body); // nothing to log here
req.end();
});
};
module.exports = {
search: async (search) => {
if (subscriptionKey.length === 32) {
//did not change anything bing_web_search returns a promise
// so you can just await it
const result = await bing_web_search(search);
console.log('Search Completed');
//this will resolve with the results
return result
} else {
console.log('Invalid Bing Search API subscription key!');
console.log('Please paste yours into the source code.');
//the caller of this function can handle the rejection
return Promise.reject('Invalid Bing Search API subscription key!');
}
},
};
<强> [更新]
您的评论建议您不要正确调用搜索或处理它正确返回的承诺。在第一个请求最后返回的一组响应中，您无法控制响应所需的时间。这就是你有Promise.all
的原因const searchObjects = [s1,s2];
const Fail = function(reason){this.reason=reason;};
Promise.all(
searchObjects.map(
searchObject => obj.search(searchObject)
.then(
x=>[x,searchObject]//if resolve just pass result
,err =>new Fail([err,searchObject])//if reject add a Fail object with some detail
)
)
)
.then(
results => {
console.log(
"resolved results:",
results.filter(([r,_])=>(r&&r.constructor)!==Fail)
);
console.log(
"failed results:",
results.filter(([r,_])=>(r&&r.constructor)===Fail)
);
}
)
如果您有大量搜索，那么您可能想要限制具有特定time period或active connections的响应数量。如果您需要帮助，请告诉我。