Is there a more efficient method to gather properties from an object into separate arrays without the need for using `map` twice?

Question

Is there a more efficient method to gather properties from an object into separate arrays without the need for using `map` twice?

Currently, my code block looks like this:

res.json({
    dates: rows.map(function (item) { return item.Date }),
    counts: rows.map(function (item) { return item.NewMembers })
});

While functional, I can't help but feel it is inefficient as the rows array is being iterated twice. How can I optimize this process and enhance performance by avoiding duplicate iterations?

It's worth noting that this code is built using Express, and res.json represents the response within the route.

If there are improved methodologies available in ES6 to address this issue, I have access to them.

javascript express

Answer 1

Answer №1

let data={dates:[],counts:[]}   
 rows.forEach(element => {
 data.dates.push(element.Date);
 data.counts.push(element.newMembers);

 });
res.json(data);

Answer 2

let data={dates:[],counts:[]}   
 rows.forEach(element => {
 data.dates.push(element.Date);
 data.counts.push(element.newMembers);

 });
res.json(data);

Answer 3

Answer №2

One approach is to utilize two arrays for gathering data.

var dates=[], counts = [];

rows.forEach(function (item) { 
    dates.push(item.Date);
    counts.push(item.NewMembers);
});

res.json({
    dates: dates,
    counts: counts
});

Answer 4

One approach is to utilize two arrays for gathering data.

var dates=[], counts = [];

rows.forEach(function (item) { 
    dates.push(item.Date);
    counts.push(item.NewMembers);
});

res.json({
    dates: dates,
    counts: counts
});

Answer 5

Answer №3

One way to tackle this problem is by utilizing the reduce method:

let data = [{date : 'a', member : 'b'}, {date : 'a1', member : 'b1'}, {date : 'a2', member : 'b2'}];

let result = data.reduce( (previous, current) => { 
  previous.date.push(current.date); 
  previous.member.push(current.member); 
  return previous;
}, { date : [], member : [] } );

console.log(result);

Answer 6

One way to tackle this problem is by utilizing the reduce method:

let data = [{date : 'a', member : 'b'}, {date : 'a1', member : 'b1'}, {date : 'a2', member : 'b2'}];

let result = data.reduce( (previous, current) => { 
  previous.date.push(current.date); 
  previous.member.push(current.member); 
  return previous;
}, { date : [], member : [] } );

console.log(result);

Is there a more efficient method to gather properties from an object into separate arrays without the need for using `map` twice?

Answer №1

Answer №2

Answer №3

Similar questions

Integrating Braintree with Angular for accepting Android Pay transactions

Integrate a button following the first paragraph exclusively when there are two or more paragraphs present

Argument for setInterval function

The issue of a non-firing Ajax click event in a JavaScript file

Unable to add files to my JavaScript file

Having trouble with the chaining of AJAX calls using Promises?

Utilizing jQuery.ajax() to retrieve the child div from a separate page

Encountering issues with displaying images in React Next.js when utilizing dangerouslySetInnerHtml

Sending a variable using the onchange function in jQuery

Adjust the information within the jwt payload

What is the best way to load an ExtJS combobox with a JSON object that includes an array

Designing a unique shape geometry using THREE JS

Passport - The method req.isAuthenticated() will return true in the /login route following the local strategy, however, it will not return true in the /current-session route after using passport.authenticate

Issue with React.useEffect not functioning in Express application

Is there a way to use Javascript to determine if a string within a JSON object has been altered?

What is the best way to send the output of a function once the loop has completed?

Executing MongoDB collection operations with array filtering

How to dynamically set a computed background image in Vue 2

Creating URL Paths in Express$route Generation"

Working with MongoDB collections in JavaScript to extract and manipulate array data