Merge N arrays containing arrays in javascript

Question

I have an array which contains arrays too. this array is template

template has 2 arrays, but 2 is not fixed, it can go on N number of arrays which also contains arrays. this is what I tried:

const template = health_pack_templates.map((healthpackItem, i) => {
  return healthpackItem.health_pack_templates
});
console.log('template', template);
var c = [];
  for (var i = 0; i >= template.length; i++) {
      c.push.apply(template[i]);
  }
console.log('c',c)

c does only returns [] and not an array with 0,1,2,3,4,5,6,7,8,9 arrays inside. What am I doing wrong?

what I want to happen should be like this: [array 0,1,2,3,4,5,6,7,8,9] after it is merged.

What does apply do?

tam.dangc
– tam.dangc

2019-03-26 07:20:30 +00:00
Commented Mar 26, 2019 at 7:20 — tam.dangc
– tam.dangc, Commented Mar 26, 2019 at 7:20

User863 · Accepted Answer · 2019-03-26 07:23:53Z

6

Try using flat() method

The flat() method which creates a new array with all sub-array elements concatenated into it recursively up to the specified depth.

edited Mar 26, 2019 at 7:23

answered Mar 26, 2019 at 7:19

User863

20.1k3 gold badges20 silver badges45 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

User863 Over a year ago

@eibersji welcome!. Also, check alternatives here

Ginger Bread · Accepted Answer · 2019-03-26 07:21:29Z

3

Maybe because you wrote i>=template.length. it should brake your for loop immediately.

answered Mar 26, 2019 at 7:21

Ginger Bread

6353 gold badges13 silver badges30 bronze badges

Comments

Community · Accepted Answer · 2020-06-20 09:12:55Z

0

Merge N Arrays

There are multiple ways in javascript today to merge variable number of arrays

Option 1 is to use reduce:

let arrs = [[1, 2], [3, 4], [5, 6]];
arrs.reduce((a, b) => [...a, ...b], []);

This is a slow solution (quadratic time).

Option 2 is that you can use Lodash:

_.flatten

This merges n arrays, and does it more efficiently (linear time).

Option 3 is to use concat function on array of arrays:

[].concat(...arrs);

Which should be efficient (linear time).

Option 4 is to use .flat()

[...arrs].flat()

If there are more than 1 level of nested arrays you might need to use [...arrs].flat(2) and so on

let arrs = [[1, 2], [3, [7, 8], 4], [5, 6]];
[...arrs].flat(2)

edited Jun 20, 2020 at 9:12

CommunityBot

11 silver badge

answered Aug 7, 2019 at 18:30

user6184932

Collectives™ on Stack Overflow

Merge N arrays containing arrays in javascript

3 Answers 3

1 Comment

Comments

Merge N Arrays

Option 1 is to use reduce:

Option 2 is that you can use Lodash:

Option 3 is to use concat function on array of arrays:

Option 4 is to use .flat()

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

1 Comment

Comments

Merge N Arrays

Option 1 is to use reduce:

Option 2 is that you can use Lodash:

Option 3 is to use concat function on array of arrays:

Option 4 is to use .flat()

Comments

Your Answer

Sign up or log in

Post as a guest

Related