如何解决NodeJS-调用函数中的提取将挂起控制台
我在React客户端遇到问题,所以我使用一个更简单的单文件节点程序重现了该错误。在React客户端中,我没有得到任何数据。使用Postman,我可以执行“获取”并检索JSON数据。
有人可以帮助我让它运行而不会挂吗?
我最近在服务器端进行了gettranslations的类似功能,以便可以从一个函数调用MongoDB。 (NodeJS ASync call of MongoClient GetData routine)。我认为我的回答与我的回答相同。
我曾考虑使用“ await”,但是我不在异步函数中。在上面提到的示例中,我不需要“等待”,因为该函数使用“ .then”模式。
部分代码:
const fetch = require("node-fetch");
function getDBLanguagesAndConvertToDataTable(fromLanguage,toLanguage) {
// Todo implement from/to Language in URL below
console.log("Function: " + getFormattedTime())
return fetch('http://localhost:3001/api/gettranslations/en-US/es-MX',{
method: 'GET',headers: {
'Accept': 'application/json'
}
})
.then(function(data) {
// do something with the data
console.log("Status:",data.status)
console.log("data from DB:")
console.log(JSON.stringify(data))
console.log("data.body:")
console.log(JSON.stringify(data.json()))
// I call another function here to reshape the data,// but even with that commented out,same issue.
return data.json()
})
.catch(function(err){
console.log("Error:" + err)
throw new Error(err)
})
}
console.log("------- Test with Fetch/Get/FromWebservice -------")
console.log(getFormattedTime())
var fromLanguage = 'en-US'
var toLanguage = 'es-MX'
getDBLanguagesAndConvertToDataTable(fromLanguage,toLanguage)
.then(function (dataTable) {
console.log(getFormattedTime," Back from call fetch")
var strDataTable = JSON.stringify(dataTable,null,3);
console.log("ReactTables(): Resulting DataTable=")
console.log(strDataTable)
console.log(getFormattedTime(),"The end of tests ")
})
我运行“ node test.js”。它显示以下内容并挂起。我必须做CNTL-Break结束它。
------- Test with Fetch/Get/FromWebservice -------
2020-08-26-20-43-08
Function: 2020-08-26-20-43-08
第2部分-添加抓取后
function getDBLanguagesAndConvertToDataTable(fromLanguage,headers: {
'Accept': 'application/json','Content-Type': 'application/json'
}
})
.then(function(data) {
// do something with the data
console.log("Status:",data.status)
console.log("data from Fetch:")
console.log(JSON.stringify(data))
console.log("data.json():")
console.log(JSON.stringify(data.json()))
//var tmpDataTable = convertMongoLanguagesToDataTable(data.json())
//return tmpDataTable
return data.json()
})
.catch(function(err){
console.log("Fetch Error:" + err)
throw new Error(err)
})
}
/*
console.log("------- Test with variable data-------------")
console.log(getFormattedTime())
dataTable = convertMongoLanguagesToDataTable(dbGetResults)
var strDataTable = JSON.stringify(dataTable,3);
console.log("Resulting DataTable=")
console.log(strDataTable)
console.log("\n\n")
*/
console.log("------- Test with Fetch/Get/FromWebservice -------")
console.log(getFormattedTime())
var fromLanguage = 'en-US'
var toLanguage = 'es-MX'
getDBLanguagesAndConvertToDataTable(fromLanguage,"The end of tests ")
.catch(function (err){
console.log("call function getDBLanguagesAndConvertToDataTable error:",getFormattedTime(),"The end of tests ")
})
})
输出:
------- Test with Fetch/Get/FromWebservice -------
2020-8-26-21-31-5
Function: 2020-8-26-21-31-5
Status: 200
data from Fetch:
{"size":0,"timeout":0}
data.body:
{}
Fetch Error:TypeError: body used already for: http://localhost:3001/api/gettranslations/en-US/es-MX
(node:38732) UnhandledPromiseRejectionWarning: Error: TypeError: body used already for: http://localhost:3001/api/gettranslations/en-US/es-MX
at E:\GitHub\NealWalters\KyleShedCompanyPOC\shedco-backend\test_convert_languages_to_data_table.js:144:12
at processticksAndRejections (internal/process/task_queues.js:97:5)
(node:38732) 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(). To terminate the node process on unhandled promise rejection,use the CLI flag `--unhandled-rejections=strict` (see https://nodejs.org/api/cli.html#cli_unhandled_rejections_mode). (rejection id: 3)
(node:38732) [DEP0018] DeprecationWarning: Unhandled promise rejections are deprecated. In the future,promise rejections that are not handled will terminate the Node.js process with a non-zero exit code.
解决方法
根据上面@ jfriend00的评论,我需要在每个.then语句上添加.catch。
一旦发现问题,我就会因为尝试访问流两次而收到错误消息,所以现在我只注释掉从fetch返回的“ data”变量上的多余console.logs。 (发现此处描述的错误: https://github.com/node-fetch/node-fetch/issues/533)
到那时,我可以从控制台中的webservice看到我的JSON,并且不再挂起!
修改后的代码:
function getDBLanguagesAndConvertToDataTable(fromLanguage,toLanguage) {
// TODO implement from/to Language in URL below
console.log("Function: " + getFormattedTime())
return fetch('http://localhost:3001/api/gettranslations/en-US/es-MX',{
method: 'GET',headers: {
'Accept': 'application/json'
}
})
.then(function(data) {
// do something with the data
/*
console.log("Status:",data.status)
console.log("data from Fetch:")
console.log(JSON.stringify(data))
console.log("data.json():")
console.log(JSON.stringify(data.json()))
*/
//var tmpDataTable = convertMongoLanguagesToDataTable(data.json())
//return tmpDataTable
return data.json()
})
.catch(function(err){
console.log("Fetch Error:" + err)
throw new Error(err)
})
}
/*
console.log("------- Test with variable data-------------")
console.log(getFormattedTime())
dataTable = convertMongoLanguagesToDataTable(dbGetResults)
var strDataTable = JSON.stringify(dataTable,null,3);
console.log("Resulting DataTable=")
console.log(strDataTable)
console.log("\n\n")
*/
console.log("------- Test with Fetch/Get/FromWebservice -------")
console.log(getFormattedTime())
var fromLanguage = 'en-US'
var toLanguage = 'es-MX'
getDBLanguagesAndConvertToDataTable(fromLanguage,toLanguage)
.then(function (dataTable) {
console.log(getFormattedTime," Back from call fetch")
var strDataTable = JSON.stringify(dataTable,3);
console.log("ReactTables(): Resulting DataTable=")
console.log(strDataTable)
console.log(getFormattedTime(),"The end of tests ")
})
.catch(function (err){
console.log("call function getDBLanguagesAndConvertToDataTable error:",getFormattedTime(),"The end of tests ")
})
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