Why my Async and Await still not do the job of sequence execution

I'm a newbie to Node.js and not sure if I understood Async/Await correctly. Here's what I'm trying to do

I'm passing values to a function and I'm expecting it to work like

Step 1. add both values
Step 2. Fetch a document from db based on value from step 1
Step 3. return the document fetched from step 2.

But the result I see is

Step 1. add both values
Step 2. return undefined while db query is running
step 3. finish running query

How do I achieve desired output from this.

var someFunction = async (a,b)=>
 var k;
 try
 k = a+b; 
 catch(err)
 return(err);
 

 var document;
 try
 document = await db.collection(somecollection).findOne(_id:k)
 catch(err)
 return(err);
 
 return(document);


someFunction(4,5).then((result)=>
 console.log(result);
);

asked Nov 15 '18 at 1:59

David

106

Which database are you using? Are you sure that db.collection(somecollection).findOne(_id:k) returns a promise?

– jfriend00
Nov 15 '18 at 3:01

add a comment |

I'm a newbie to Node.js and not sure if I understood Async/Await correctly. Here's what I'm trying to do

I'm passing values to a function and I'm expecting it to work like

Step 1. add both values
Step 2. Fetch a document from db based on value from step 1
Step 3. return the document fetched from step 2.

But the result I see is

Step 1. add both values
Step 2. return undefined while db query is running
step 3. finish running query

How do I achieve desired output from this.

var someFunction = async (a,b)=>
 var k;
 try
 k = a+b; 
 catch(err)
 return(err);
 

 var document;
 try
 document = await db.collection(somecollection).findOne(_id:k)
 catch(err)
 return(err);
 
 return(document);


someFunction(4,5).then((result)=>
 console.log(result);
);

asked Nov 15 '18 at 1:59

David

106

Which database are you using? Are you sure that db.collection(somecollection).findOne(_id:k) returns a promise?

– jfriend00
Nov 15 '18 at 3:01

add a comment |

I'm a newbie to Node.js and not sure if I understood Async/Await correctly. Here's what I'm trying to do

I'm passing values to a function and I'm expecting it to work like

Step 1. add both values
Step 2. Fetch a document from db based on value from step 1
Step 3. return the document fetched from step 2.

But the result I see is

Step 1. add both values
Step 2. return undefined while db query is running
step 3. finish running query

How do I achieve desired output from this.

var someFunction = async (a,b)=>
 var k;
 try
 k = a+b; 
 catch(err)
 return(err);
 

 var document;
 try
 document = await db.collection(somecollection).findOne(_id:k)
 catch(err)
 return(err);
 
 return(document);


someFunction(4,5).then((result)=>
 console.log(result);
);

asked Nov 15 '18 at 1:59

David

106

I'm a newbie to Node.js and not sure if I understood Async/Await correctly. Here's what I'm trying to do

I'm passing values to a function and I'm expecting it to work like

Step 1. add both values
Step 2. Fetch a document from db based on value from step 1
Step 3. return the document fetched from step 2.

But the result I see is

Step 1. add both values
Step 2. return undefined while db query is running
step 3. finish running query

How do I achieve desired output from this.

var someFunction = async (a,b)=>
 var k;
 try
 k = a+b; 
 catch(err)
 return(err);
 

 var document;
 try
 document = await db.collection(somecollection).findOne(_id:k)
 catch(err)
 return(err);
 
 return(document);


someFunction(4,5).then((result)=>
 console.log(result);
);

javascript angularjs node.js async-await

asked Nov 15 '18 at 1:59

David

106

asked Nov 15 '18 at 1:59

David

106

asked Nov 15 '18 at 1:59

David

106

asked Nov 15 '18 at 1:59

David

106

asked Nov 15 '18 at 1:59

David

106

Which database are you using? Are you sure that db.collection(somecollection).findOne(_id:k) returns a promise?

– jfriend00
Nov 15 '18 at 3:01

add a comment |

Which database are you using? Are you sure that db.collection(somecollection).findOne(_id:k) returns a promise?

– jfriend00
Nov 15 '18 at 3:01

Which database are you using? Are you sure that db.collection(somecollection).findOne(_id:k) returns a promise?

– jfriend00
Nov 15 '18 at 3:01

add a comment |

1 Answer
1

active

oldest

votes

findone may return undefined if no match found
findOne returns undefined on the server

In the first try...catch block, why do you worry about an exception of adding two variables? that never result on error in javascript.

Also make sure you're passing the _id correctly to findone, Mongo uses UUID to calculate _id and I don't think that can be returned from adding a + b

edited Nov 15 '18 at 2:18

answered Nov 15 '18 at 2:12

doc_id

890931

This is an example I've taken here in real the first try will have much more to do. in the second block document exists but takes time to run the query, if I print the document in second block it prints moments later undefined is printed which shows that return statement is executed before the second block is finished executing.

– David
Nov 15 '18 at 2:28

try to cast k to ObjectId, add var ObjectId = require('mongodb').ObjectId in top and then await db.collection(somecollection).findOne(_id: new ObjectId(k) )

– doc_id
Nov 15 '18 at 4:47

add a comment |

Your Answer

StackExchange.ifUsing("editor", function ()
StackExchange.using("externalEditor", function ()
StackExchange.using("snippets", function ()
StackExchange.snippets.init();
);
);
, "code-snippets");

StackExchange.ready(function()
var channelOptions =
tags: "".split(" "),
id: "1"
;
initTagRenderer("".split(" "), "".split(" "), channelOptions);

StackExchange.using("externalEditor", function()
// Have to fire editor after snippets, if snippets enabled
if (StackExchange.settings.snippets.snippetsEnabled)
StackExchange.using("snippets", function()
createEditor();
);

else
createEditor();

);

function createEditor()
StackExchange.prepareEditor(
heartbeatType: 'answer',
autoActivateHeartbeat: false,
convertImagesToLinks: true,
noModals: true,
showLowRepImageUploadWarning: true,
reputationToPostImages: 10,
bindNavPrevention: true,
postfix: "",
imageUploader:
brandingHtml: "Powered by u003ca class="icon-imgur-white" href="https://imgur.com/"u003eu003c/au003e",
contentPolicyHtml: "User contributions licensed under u003ca href="https://creativecommons.org/licenses/by-sa/3.0/"u003ecc by-sa 3.0 with attribution requiredu003c/au003e u003ca href="https://stackoverflow.com/legal/content-policy"u003e(content policy)u003c/au003e",
allowUrls: true
,
onDemand: true,
discardSelector: ".discard-answer"
,immediatelyShowMarkdownHelp:true
);

);

draft saved

draft discarded

StackExchange.ready(
function ()
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fstackoverflow.com%2fquestions%2f53311362%2fwhy-my-async-and-await-still-not-do-the-job-of-sequence-execution%23new-answer', 'question_page');

);

Post as a guest

Name

Required, but never shown

1 Answer
1

active

oldest

votes

1 Answer
1

active

oldest

votes

findone may return undefined if no match found
findOne returns undefined on the server

In the first try...catch block, why do you worry about an exception of adding two variables? that never result on error in javascript.

Also make sure you're passing the _id correctly to findone, Mongo uses UUID to calculate _id and I don't think that can be returned from adding a + b

edited Nov 15 '18 at 2:18

answered Nov 15 '18 at 2:12

doc_id

890931

This is an example I've taken here in real the first try will have much more to do. in the second block document exists but takes time to run the query, if I print the document in second block it prints moments later undefined is printed which shows that return statement is executed before the second block is finished executing.

– David
Nov 15 '18 at 2:28

try to cast k to ObjectId, add var ObjectId = require('mongodb').ObjectId in top and then await db.collection(somecollection).findOne(_id: new ObjectId(k) )

– doc_id
Nov 15 '18 at 4:47

add a comment |

findone may return undefined if no match found
findOne returns undefined on the server

In the first try...catch block, why do you worry about an exception of adding two variables? that never result on error in javascript.

Also make sure you're passing the _id correctly to findone, Mongo uses UUID to calculate _id and I don't think that can be returned from adding a + b

edited Nov 15 '18 at 2:18

answered Nov 15 '18 at 2:12

doc_id

890931

This is an example I've taken here in real the first try will have much more to do. in the second block document exists but takes time to run the query, if I print the document in second block it prints moments later undefined is printed which shows that return statement is executed before the second block is finished executing.

– David
Nov 15 '18 at 2:28

try to cast k to ObjectId, add var ObjectId = require('mongodb').ObjectId in top and then await db.collection(somecollection).findOne(_id: new ObjectId(k) )

– doc_id
Nov 15 '18 at 4:47

add a comment |

findone may return undefined if no match found
findOne returns undefined on the server

In the first try...catch block, why do you worry about an exception of adding two variables? that never result on error in javascript.

Also make sure you're passing the _id correctly to findone, Mongo uses UUID to calculate _id and I don't think that can be returned from adding a + b

edited Nov 15 '18 at 2:18

answered Nov 15 '18 at 2:12

doc_id

890931

findone may return undefined if no match found
findOne returns undefined on the server

In the first try...catch block, why do you worry about an exception of adding two variables? that never result on error in javascript.

Also make sure you're passing the _id correctly to findone, Mongo uses UUID to calculate _id and I don't think that can be returned from adding a + b

edited Nov 15 '18 at 2:18

answered Nov 15 '18 at 2:12

doc_id

890931

edited Nov 15 '18 at 2:18

answered Nov 15 '18 at 2:12

doc_id

890931

answered Nov 15 '18 at 2:12

doc_id

890931

answered Nov 15 '18 at 2:12

doc_id

890931

This is an example I've taken here in real the first try will have much more to do. in the second block document exists but takes time to run the query, if I print the document in second block it prints moments later undefined is printed which shows that return statement is executed before the second block is finished executing.

– David
Nov 15 '18 at 2:28

try to cast k to ObjectId, add var ObjectId = require('mongodb').ObjectId in top and then await db.collection(somecollection).findOne(_id: new ObjectId(k) )

– doc_id
Nov 15 '18 at 4:47

add a comment |

This is an example I've taken here in real the first try will have much more to do. in the second block document exists but takes time to run the query, if I print the document in second block it prints moments later undefined is printed which shows that return statement is executed before the second block is finished executing.

– David
Nov 15 '18 at 2:28

try to cast k to ObjectId, add var ObjectId = require('mongodb').ObjectId in top and then await db.collection(somecollection).findOne(_id: new ObjectId(k) )

– doc_id
Nov 15 '18 at 4:47

This is an example I've taken here in real the first try will have much more to do. in the second block document exists but takes time to run the query, if I print the document in second block it prints moments later undefined is printed which shows that return statement is executed before the second block is finished executing.

– David
Nov 15 '18 at 2:28

try to cast k to ObjectId, add var ObjectId = require('mongodb').ObjectId in top and then await db.collection(somecollection).findOne(_id: new ObjectId(k) )

– doc_id
Nov 15 '18 at 4:47

add a comment |

draft saved

draft discarded

Thanks for contributing an answer to Stack Overflow!

Please be sure to answer the question. Provide details and share your research!

But avoid …

Asking for help, clarification, or responding to other answers.

Making statements based on opinion; back them up with references or personal experience.

To learn more, see our tips on writing great answers.

draft saved

draft discarded

Post as a guest

Name

Required, but never shown

Name

Required, but never shown

Name

Required, but never shown

This page is only for reference, If you need detailed information, please check here

搜尋此網誌

Pfthb