Otdfbt

How to edit “Name” property in GCI output?

Does Germany produce more waste than the US?

Is wanting to ask what to write an indication that you need to change your story?

Flying from Cape Town to England and return to another province

Math-accent symbol over parentheses enclosing accented symbol (amsmath)

Why is my new battery behaving weirdly?

I want to delete every two lines after 3rd lines in file contain very large number of lines :

I believe this to be a fraud - hired, then asked to cash check and send cash as Bitcoin

Do I need to write [sic] when a number is less than 10 but isn't written out?

What happened in Rome, when the western empire "fell"?

Would be okay to drive on this tire?

A Man With a Stainless Steel Endoskeleton (like The Terminator) Fighting Cloaked Aliens Only He Can See

How many extra stops do monopods offer for tele photographs?

The exact meaning of 'Mom made me a sandwich'

Grabbing quick drinks

RigExpert AA-35 - Interpreting The Information

How to check if all elements of 1 list are in the *same quantity* and in any order, in the list2?

How to get from Geneva Airport to Metabief, Doubs, France by public transport?

Is there a difference between "Fahrstuhl" and "Aufzug"

Running a General Election and the European Elections together

When you upcast Blindness/Deafness, do all targets suffer the same effect?

Why is quantifier elimination desirable for a given theory?

How to count occurrences of text in a file?

Why the difference in type-inference over the as-pattern in two similar function definitions?

Reduce array of object to totals by property object

7

0

I'm looking for a smart ES6 way to reduce array of objects into totals-by-property-object.

for a sample data:

const src = [mon:1,tue:0,wed:3,thu:5,fri:7,sat:0,sun:4, mon:5,tue:3,wed:2,thu:0,fri:1,sat:0,sun:6];

following code:

const res = src.reduce((totals,item) => Object.keys(item).forEach(weekday => totals[weekday] += item[weekday]),)

throws an error:

Uncaught TypeError: Cannot read property 'mon' of undefined

even if reduce is initialized with mon:0, tue:0 ... instead of .

Is there a non-for-loop solution?

p.s. expected output is an object where each property is a sum of array objects by that property, e.g. mon:6, tue:3, wed:5, thu:5, fri:8, sat:0, sun:10 in my case

javascript ecmascript-6

share|improve this question

edited yesterday

user11154868

asked yesterday

user11154868user11154868

384

New contributor

user11154868 is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

add a comment | 

7

0

I'm looking for a smart ES6 way to reduce array of objects into totals-by-property-object.

for a sample data:

const src = [mon:1,tue:0,wed:3,thu:5,fri:7,sat:0,sun:4, mon:5,tue:3,wed:2,thu:0,fri:1,sat:0,sun:6];

following code:

const res = src.reduce((totals,item) => Object.keys(item).forEach(weekday => totals[weekday] += item[weekday]),)

throws an error:

Uncaught TypeError: Cannot read property 'mon' of undefined

even if reduce is initialized with mon:0, tue:0 ... instead of .

Is there a non-for-loop solution?

p.s. expected output is an object where each property is a sum of array objects by that property, e.g. mon:6, tue:3, wed:5, thu:5, fri:8, sat:0, sun:10 in my case

javascript ecmascript-6

share|improve this question

edited yesterday

user11154868

asked yesterday

user11154868user11154868

384

New contributor

user11154868 is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

add a comment | 

I'm looking for a smart ES6 way to reduce array of objects into totals-by-property-object.

for a sample data:

const src = [mon:1,tue:0,wed:3,thu:5,fri:7,sat:0,sun:4, mon:5,tue:3,wed:2,thu:0,fri:1,sat:0,sun:6];

following code:

const res = src.reduce((totals,item) => Object.keys(item).forEach(weekday => totals[weekday] += item[weekday]),)

throws an error:

Uncaught TypeError: Cannot read property 'mon' of undefined

even if reduce is initialized with mon:0, tue:0 ... instead of .

Is there a non-for-loop solution?

p.s. expected output is an object where each property is a sum of array objects by that property, e.g. mon:6, tue:3, wed:5, thu:5, fri:8, sat:0, sun:10 in my case

javascript ecmascript-6

share|improve this question

edited yesterday

user11154868

asked yesterday

user11154868user11154868

384

New contributor

user11154868 is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

const src = [mon:1,tue:0,wed:3,thu:5,fri:7,sat:0,sun:4, mon:5,tue:3,wed:2,thu:0,fri:1,sat:0,sun:6];

const res = src.reduce((totals,item) => Object.keys(item).forEach(weekday => totals[weekday] += item[weekday]),)

share|improve this question

edited yesterday

user11154868

asked yesterday

user11154868user11154868

384

New contributor

user11154868 is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

share|improve this question

edited yesterday

user11154868

asked yesterday

user11154868user11154868

384

New contributor

user11154868 is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

asked yesterday

user11154868user11154868

384

New contributor

user11154868 is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

asked yesterday

user11154868user11154868

384

2 Answers
2

active

oldest

votes

5

You need to return totals after you modify it:

const src = [mon:1,tue:0,wed:3,thu:5,fri:7,sat:0,sun:4, mon:5,tue:3,wed:2,thu:0,fri:1,sat:0,sun:6];

const res = src.reduce((totals, item) => 0) + item[weekday])
 
 return totals;
, );

console.log(res);

share|improve this answer

answered yesterday

Ori DroriOri Drori

81.4k138997

• 
  
  
  

  
  3
  

  
  
  
  
  
  

  
  
  I can't believe it was that close. Thanks a lot.
  
  – user11154868
  yesterday
  

  
  
  
  

add a comment | 

4

You need to return totals as accumulator for reduce.

If you have allways all days in the objects and you don't mind to mutate the first object, you could work without a start object.

const
 src = [ mon: 1, tue: 0, wed: 3, thu: 5, fri: 7, sat: 0, sun: 4 , mon: 5, tue: 3, wed: 2, thu: 0, fri: 1, sat: 0, sun: 6 ],
 res = src.reduce((totals, item) => 
 (Object.keys(item).forEach(d => totals[d] += item[d]), totals));

console.log(res);

share|improve this answer

answered yesterday

Nina ScholzNina Scholz

195k15107178

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
);



);

user11154868 is a new contributor. Be nice, and check out our Code of Conduct.

draft saved

draft discarded

Sign up or log in

StackExchange.ready(function ()
StackExchange.helpers.onClickDraftSave('#login-link');
);

Sign up using Google

Sign up using Facebook

Sign up using Email and Password

Post as a guest

Name

Email

Required, but never shown

StackExchange.ready(
function ()
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fstackoverflow.com%2fquestions%2f55418223%2freduce-array-of-object-to-totals-by-property-object%23new-answer', 'question_page');

);

Post as a guest

Name

Email

Required, but never shown

5

You need to return totals after you modify it:

const src = [mon:1,tue:0,wed:3,thu:5,fri:7,sat:0,sun:4, mon:5,tue:3,wed:2,thu:0,fri:1,sat:0,sun:6];

const res = src.reduce((totals, item) => 0) + item[weekday])
 
 return totals;
, );

console.log(res);

share|improve this answer

answered yesterday

Ori DroriOri Drori

81.4k138997

• 
  
  
  

  
  3
  

  
  
  
  
  
  

  
  
  I can't believe it was that close. Thanks a lot.
  
  – user11154868
  yesterday
  

  
  
  
  

add a comment | 

5

You need to return totals after you modify it:

const src = [mon:1,tue:0,wed:3,thu:5,fri:7,sat:0,sun:4, mon:5,tue:3,wed:2,thu:0,fri:1,sat:0,sun:6];

const res = src.reduce((totals, item) => 0) + item[weekday])
 
 return totals;
, );

console.log(res);

share|improve this answer

answered yesterday

Ori DroriOri Drori

81.4k138997

• 
  
  
  

  
  3
  

  
  
  
  
  
  

  
  
  I can't believe it was that close. Thanks a lot.
  
  – user11154868
  yesterday
  

  
  
  
  

add a comment | 

You need to return totals after you modify it:

const src = [mon:1,tue:0,wed:3,thu:5,fri:7,sat:0,sun:4, mon:5,tue:3,wed:2,thu:0,fri:1,sat:0,sun:6];

const res = src.reduce((totals, item) => 0) + item[weekday])
 
 return totals;
, );

console.log(res);

share|improve this answer

answered yesterday

Ori DroriOri Drori

81.4k138997

const src = [mon:1,tue:0,wed:3,thu:5,fri:7,sat:0,sun:4, mon:5,tue:3,wed:2,thu:0,fri:1,sat:0,sun:6];

const res = src.reduce((totals, item) => 0) + item[weekday])
 
 return totals;
, );

console.log(res);

const src = [mon:1,tue:0,wed:3,thu:5,fri:7,sat:0,sun:4, mon:5,tue:3,wed:2,thu:0,fri:1,sat:0,sun:6];

const res = src.reduce((totals, item) => 0) + item[weekday])
 
 return totals;
, );

console.log(res);

const src = [mon:1,tue:0,wed:3,thu:5,fri:7,sat:0,sun:4, mon:5,tue:3,wed:2,thu:0,fri:1,sat:0,sun:6];

const res = src.reduce((totals, item) => 0) + item[weekday])
 
 return totals;
, );

console.log(res);

share|improve this answer

answered yesterday

Ori DroriOri Drori

81.4k138997

answered yesterday

Ori DroriOri Drori

81.4k138997

answered yesterday

Ori DroriOri Drori

81.4k138997

4

You need to return totals as accumulator for reduce.

If you have allways all days in the objects and you don't mind to mutate the first object, you could work without a start object.

const
 src = [ mon: 1, tue: 0, wed: 3, thu: 5, fri: 7, sat: 0, sun: 4 , mon: 5, tue: 3, wed: 2, thu: 0, fri: 1, sat: 0, sun: 6 ],
 res = src.reduce((totals, item) => 
 (Object.keys(item).forEach(d => totals[d] += item[d]), totals));

console.log(res);

share|improve this answer

answered yesterday

Nina ScholzNina Scholz

195k15107178

add a comment | 

4

You need to return totals as accumulator for reduce.

If you have allways all days in the objects and you don't mind to mutate the first object, you could work without a start object.

const
 src = [ mon: 1, tue: 0, wed: 3, thu: 5, fri: 7, sat: 0, sun: 4 , mon: 5, tue: 3, wed: 2, thu: 0, fri: 1, sat: 0, sun: 6 ],
 res = src.reduce((totals, item) => 
 (Object.keys(item).forEach(d => totals[d] += item[d]), totals));

console.log(res);

share|improve this answer

answered yesterday

Nina ScholzNina Scholz

195k15107178

add a comment | 

You need to return totals as accumulator for reduce.

If you have allways all days in the objects and you don't mind to mutate the first object, you could work without a start object.

const
 src = [ mon: 1, tue: 0, wed: 3, thu: 5, fri: 7, sat: 0, sun: 4 , mon: 5, tue: 3, wed: 2, thu: 0, fri: 1, sat: 0, sun: 6 ],
 res = src.reduce((totals, item) => 
 (Object.keys(item).forEach(d => totals[d] += item[d]), totals));

console.log(res);

share|improve this answer

answered yesterday

Nina ScholzNina Scholz

195k15107178

const
 src = [ mon: 1, tue: 0, wed: 3, thu: 5, fri: 7, sat: 0, sun: 4 , mon: 5, tue: 3, wed: 2, thu: 0, fri: 1, sat: 0, sun: 6 ],
 res = src.reduce((totals, item) => 
 (Object.keys(item).forEach(d => totals[d] += item[d]), totals));

console.log(res);

const
 src = [ mon: 1, tue: 0, wed: 3, thu: 5, fri: 7, sat: 0, sun: 4 , mon: 5, tue: 3, wed: 2, thu: 0, fri: 1, sat: 0, sun: 6 ],
 res = src.reduce((totals, item) => 
 (Object.keys(item).forEach(d => totals[d] += item[d]), totals));

console.log(res);

const
 src = [ mon: 1, tue: 0, wed: 3, thu: 5, fri: 7, sat: 0, sun: 4 , mon: 5, tue: 3, wed: 2, thu: 0, fri: 1, sat: 0, sun: 6 ],
 res = src.reduce((totals, item) => 
 (Object.keys(item).forEach(d => totals[d] += item[d]), totals));

console.log(res);

share|improve this answer

answered yesterday

Nina ScholzNina Scholz

195k15107178

answered yesterday

Nina ScholzNina Scholz

195k15107178

answered yesterday

Nina ScholzNina Scholz

195k15107178