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
– Prakhar Londhe, Commented Feb 20, 2020 at 9:20
Does this answer your question? For-each over an array in JavaScript? — Smit Patel
– Smit Patel, Commented Feb 20, 2020 at 9:20
You are talking about a stream object yet your array look pretty standard to me. Could you include a minimal reproducible example with your issue? — Ulysse BN
– Ulysse BN, Commented Feb 20, 2020 at 9:29

Jonathan Irwin · Accepted Answer · 2020-02-20 09:35:37Z

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, 2020 at 9:35

Jonathan Irwin

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Comments

harsh_apache · Accepted Answer · 2020-02-20 09:58:58Z

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, 2020 at 9:58

harsh_apache

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2 Comments

harsh_apache Over a year ago

@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

Rajat Srivastava Over a year ago

Ya you are right, It also worked for me than you and it is much more readable and understandable. Thanx

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