Promise是解决每个“if”条件，而不是只返回一个条件
Promise是解决每个“if”条件，而不是只返回一个条件
提问于 2020-09-24 20:49:23
我正在尝试返回一个特定的响应，这取决于我获得的一些数据。问题是，每次它都会返回最后一个响应，即使它已经通过了正确的条件：
api.get('/database-manager/request-status', async (lambdaRequest, lambdaResponse, next) => {
if (connectionPool == null) {
connectionPool = await mySQLConnectionPool();
}
requestId = lambdaRequest.headers["request-id"]
const res = await new Promise(
async function (resolve, reject) {
await getRequests()
for (let index in requestIds) {
console.log(`requestId in header : ${requestId}`)
if (requestId == requestIds[index].request_id) {
console.log(`id in list : ${requestIds[index].request_id}`)
requestStatus = requestIds[index].request_status
console.log("am in the first if ")
if (requestStatus == 'Finished') {
console.log("am in the finished if ")
ec2InstanceLink = requestIds[index].instance_link
let response = {
"statusCode": 200,
"headers": {},
"isBase64Encoded": false,
"body": ec2InstanceLink
}
resolve(response)
} else {
console.log("am in the not finished if ")
let response = {
"statusCode": 200,
"headers": {},
"isBase64Encoded": false,
"body": JSON.stringify({status: requestStatus})
}
resolve(response)
}
}
console.log("cannot find")
let response = {
"statusCode": 200,
"headers": {},
"isBase64Encoded": false,
"body": "Request-Id doesn't exist"
}
resolve(response)
}
}
)
return res;
}
)这是控制台日志，证明即使它处于正确的情况，它也没有返回正确的响应。：
1600950719600 START RequestId: 3436e868-b36f-4d51-88c0-0c6b3d06bbb7 Version: $LATEST
1600950721777 2020-09-24T12:32:01.777Z 3436e868-b36f-4d51-88c0-0c6b3d06bbb7 INFO requestId in header : 911e8b872dbe7fc8a2821008bf8af87c
1600950721795 2020-09-24T12:32:01.777Z 3436e868-b36f-4d51-88c0-0c6b3d06bbb7 INFO cannot find
1600950721815 2020-09-24T12:32:01.815Z 3436e868-b36f-4d51-88c0-0c6b3d06bbb7 INFO requestId in header : 911e8b872dbe7fc8a2821008bf8af87c
1600950721815 2020-09-24T12:32:01.815Z 3436e868-b36f-4d51-88c0-0c6b3d06bbb7 INFO id in list : 911e8b872dbe7fc8a2821008bf8af87c
1600950721815 2020-09-24T12:32:01.815Z 3436e868-b36f-4d51-88c0-0c6b3d06bbb7 INFO am in the first if
1600950721815 2020-09-24T12:32:01.815Z 3436e868-b36f-4d51-88c0-0c6b3d06bbb7 INFO am in the not finished if
1600950721815 2020-09-24T12:32:01.815Z 3436e868-b36f-4d51-88c0-0c6b3d06bbb7 INFO cannot find
1600950721815 2020-09-24T12:32:01.815Z 3436e868-b36f-4d51-88c0-0c6b3d06bbb7 INFO requestId in header : 911e8b872dbe7fc8a2821008bf8af87c
1600950721815 2020-09-24T12:32:01.815Z 3436e868-b36f-4d51-88c0-0c6b3d06bbb7 INFO cannot find
1600950721836 END RequestId: 3436e868-b36f-4d51-88c0-0c6b3d06bbb7
1600950721836 REPORT RequestId: 3436e868-b36f-4d51-88c0-0c6b3d06bbb7 Duration: 2235.83 ms Billed Duration: 2300 ms Memory Size: 128 MB Max Memory Used: 94 MB Init Duration: 529.96 ms回答 1
Stack Overflow用户
发布于 2020-09-24 21:21:04
问题是您多次调用resolve，但只有第一次有效。
结构简化：
await new Promise(
async function (resolve, reject) {
for (...) {
if (...) {
if (...) {
resolve(response)
} else {
resolve(response)
}
}
resolve(response)
}
}
)在for循环的每次迭代中都会调用resolve，并且promises只能解析一次。因为代码是同步的，所以它将处理所有的请求ids，但await new Promise的结果将是第一个响应，即Request-Id doesn't exist。
这就是为什么你会看到一个错误的响应。要解决此问题，您只需解析promise一次。如何做到这一点取决于您想要实现什么，如果您搜索匹配的responseId，那么只需将最后一个resolve移出for循环即可。
页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/64046810
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