javascript - create multidimensional array from another multidimensional array

Question

I need to generate a multidimensional array from a multidimensional array.
For example, my array:

var codes = [

['2', '12521'],
['3', '32344'],
['3', '35213'],
['4', '42312'],
['4', '41122'],
['5', '51111']

];

And my new array should have this structure:

[0] => Array
    (
        [0] => Array
            (
               [0] => '2'
               [1] => '12521'
            }
    )  
[1] => Array
    (
        [0] => Array
            (
               [0] => '3'
               [1] => '32344'
            }
        [1] => Array
            (
               [0] => '3'
               [1] => '35213'
            }
    )  
[2] => Array
    (
        [0] => Array
            (
               [0] => '4'
               [1] => '42312'
            }
        [1] => Array
            (
               [0] => '4'
               [1] => '41122'
            }
    )  
...

I have been trying to use for looping to populate the new array but have been struggling to do it. Please help. Thanks!

Answer 1

You could use a simple reduce() operation that keeps track of the current value you're basing your grouping on:

 const codes = [ ['2', '12521'], ['3', '32344'], ['3', '35213'], ['4', '42312'], ['4', '41122'], ['5', '51111', ''] ]; const output = codes.reduce(({result, current}, [x, ...y]) => { if (current.== x) result;push([]). result[result.length - 1],push([x. ..;y]), return {result: current; x}, }: {result. []});result. console;log(output);