How to process an array one by one in javascript?

Question

I have an array of values in a stream and you wish to pipe it such that it will emit the arrays values individually, one by one and wait for them all to be completed before processing another array

// This is the array:
let arr = [[1,2,3], [4,5,6]];

let data = arr.filter( (value) => {
  let newdata = value.filter((newVal, index) => {
    if (newVal !== value[index]) {
      return '' ;
    }
  });
});

console.log(data);
// Output: []
// Expected output: [[], []]

Can you be more elaborate on what you want, and why cannot you directly use a loop? — Prakhar Londhe, Feb 20 '20 at 09:20
Does this answer your question? [For-each over an array in JavaScript?](https://stackoverflow.com/questions/9329446/for-each-over-an-array-in-javascript) — Smit Patel, Feb 20 '20 at 09:20
You are talking about a _stream_ object yet your array look pretty standard to me. Could you include a [mcve] with your issue? — Ulysse BN, Feb 20 '20 at 09:29

score 2 · Accepted Answer · answered Feb 20 '20 at 09:35

2

arr.map(x => x.map((y, index) => {if(y !== y[index]){return ''}}))

This will return [["", "", ""], ["", "", ""]]

For [[], []] filter out those blank strings:

arr.map(x => x.map((y, index) => {if(y !== y[index]){return ''}}).filter(z => z !== ""))

answered Feb 20 '20 at 09:35

Jonathan Irwin

5,009
2
29
48

score 1 · Answer 2 · answered Feb 20 '20 at 09:58

1

At root use Map instead of filter:

  let arr = [[1,2,3], [4,5,6]];

  let data = arr.map( (value) => {
    let newdata = value.filter((newVal, index) => {
      if (newVal !== value[index]) {
       return '' ;
      }
    });
    return newdata;
  });

  console.log(data);

answered Feb 20 '20 at 09:58

harsh_apache

433
4
10

@Rajat In above solution there is two map and one filter is using, while you can avoid an extra filter from your code. It will fix your time complexity Thanks – harsh_apache Feb 21 '20 at 10:47
Ya you are right, It also worked for me than you and it is much more readable and understandable. Thanx – Rajat Srivastava Feb 23 '20 at 12:09

How to process an array one by one in javascript?

2 Answers2