Create a new array by getting the first value of each array

Question

I have an array of arrays like this

[
 [2, 0, 0, 2, 0],
 [4, 0, 0, 0, 1],
 [1, 1, 0, 0, 0],
 [1, 0, 1, 0, 0]
]

And I am trying to create a new array by getting the first value of each array so the output will be

[
 [2, 4, 1, 1],
 [0, 0, 1, 0],
 [0, 0, 0, 1],
 [2, 0, 0, 0],
 [0, 1, 0, 0]
]

Is there any workarounds to achieve it? Thanks

A loop should do the job. So... What have you tried so far to solve this on your own? — Andreas, Nov 05 '20 at 08:11
I haven't tried anything, I thought it would be more complexed than a loop, thanks for the help anyway ! — Kaung Khant Zaw, Nov 05 '20 at 08:19

score 1 · Accepted Answer · answered Nov 05 '20 at 08:13

1

Looping based on the subarray length, using Array.prototype.flatMap, you can get the array of the ith item of child array as a new array.

const input = [
  [2, 0, 0, 2, 0],
  [4, 0, 0, 0, 1],
  [1, 1, 0, 0, 0],
  [1, 0, 1, 0, 0]
];

const output = [];
for (let i = 0; i < input[0].length; i ++) {
  output.push(input.flatMap(item => item[i]));
}

console.log(output);

answered Nov 05 '20 at 08:13

Derek Wang

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Thanks ! I will accept answer once I am not in cooldown – Kaung Khant Zaw Nov 05 '20 at 08:19
@KaungKhantZaw is it just a typo that your input is `4*5` matrix and the output is `4*4` matrix? – Alan Omar Nov 05 '20 at 10:03
@AlanOmar It's a typo, I fixed it, thanks. – Kaung Khant Zaw Nov 05 '20 at 10:53

Create a new array by getting the first value of each array

1 Answers1