How to shift 1 element of 3D array

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For example, I want to shift 1 element of arrays:

1D array:

const arr_1d=["a","b","c","d"];
arr_1d.push(arr_1d.shift())
document.write(JSON.stringify(arr_1d)); //["b","c","d","a"]

2D array:

const arr_2d=[["a","b"],["c","d"]];
for(let i=0;i<arr_2d.length;i++){
  arr_2d[i==0?arr_2d.length-1:i-1].push(arr_2d[i].shift());
}
document.write(JSON.stringify(arr_2d)); //[["b","c"],["d","a"]]

How to I do it with 3D array

// (eg:
  [[["a","b"],[["c","d"]],[["e","f"],[["g","h"]]] 
// to 
  [[["b","c"],[["d","e"]],[["f","g"],[["h","a"]]]  
//)

I tried:

const arr_3d=[[["a","b"],["c","d"]],[["e","f"],["g","h"]]];
for(let i=0;i<arr_3d.length;i++){
  for(let j=0;j<arr_3d[i].length;j++){
      arr_3d[i][j==0?arr_3d.length-1:j-1].push(arr_3d[i][j].shift());
  }
}
document.write(JSON.stringify(arr_3d)); //[[["b","c"],["d","a"]],[["f","g"],["h","e"]]]

the output is

[[["b","c"],["d","a"]],[["f","g"],["h","e"]]]

instead of

[[["b","c"],[["d","e"]],[["f","g"],[["h","a"]]]

, which is not working.

multidimensional-array arrays javascript
4 Answers

The following should do it:

const arr_3d=
[
 [
  ["a","b"],
  ["c","d"]
 ],
 [
  ["e","f"],
  ["g","h"]
 ]
];
const one=arr_3d.flat(2); // flatten
one.push(one.shift()); // rotate values
const three=arr_3d.forEach(a3=>
 a3.forEach(a2=>
  a2.forEach((_,i,a)=>
   a[i]=one.shift()))); // feed back

document.write(JSON.stringify(arr_3d));

I simply flatten the whole array into a new one dimensional array one, "rotate" the values there once and then feed the elements back into the already existing array arr_3d, replacing the original values there.

Carsten Massmann0

Adding to the @Carsten-Massmann answer, we can also create a recursive function to achieve n level of shifting of array items.

const arr_1d = ['a', 'b', 'c'],
      arr_2d = [["a","b"],["c","d"],["e","f"],["g","h"]],
      arr_3d = [[['a','b'],['c','d']],[['e','f'],['g','h']]];
      

const flattenArray = a => (a=a.flat(Infinity), a.push(a.shift()), a);

const mappedArr = (a,f) => a.map(o=> Array.isArray(o) ? mappedArr(o,f) : f.shift())

console.log(JSON.stringify(mappedArr(arr_1d, flattenArray(arr_1d))));
console.log(JSON.stringify(mappedArr(arr_2d, flattenArray(arr_2d))));
console.log(JSON.stringify(mappedArr(arr_3d, flattenArray(arr_3d))));

gorak0

This code give you the expected answer.In here I flatten the whole 3d arr and re assign that element to the correct position according to the shift order.

const arr_3d=[[["a","b"],["c","d"]],[["e","f"],["g","h"]]];
const tmp=[]
for(let i=0;i<arr_3d.length;i++){
  for(let j=0;j<arr_3d[i].length;j++){
     for(let k=0; k<arr_3d[i][j].length;k++){
       tmp.push(arr_3d[i][j][k])
     }
        
  }
}

n=1
for(let i=0;i<arr_3d.length;i++){
  for(let j=0;j<arr_3d[i].length;j++){
     for(let k=0; k<arr_3d[i][j].length;k++){
       arr_3d[i][j][k]=tmp[n%tmp.length]
       n+=1
     }
        
  }
}
document.write(JSON.stringify(arr_3d));

YJR0

this one work in any dimensions...

const
  arr_1d = ['a','b','c','d']
, arr_2d = [['a','b'],['c','d']]
, arr_3d = [[['a','b'],['c','d']],[['e','f'],['g','h']]]
  ;

console.log( JSON.stringify( universalShift(arr_1d) ) )
console.log( JSON.stringify( universalShift(arr_2d) ) )
console.log( JSON.stringify( universalShift(arr_3d) ) )


function universalShift( arrXdim )
  {
  let shift=null, lastPath=null, indx=0;
  parse(arrXdim)
  if (lastPath) setLast( lastPath, shift );

  return arrXdim;

  function parse(arr, sPath='[]', level=0)
    {
    let path = JSON.parse(sPath);
    for(let i=0;i<arr.length;i++)
      {
      path[level] = i;
      if (Array.isArray(arr[i]))  
        parse(arr[i], JSON.stringify(path), level +1 );
      else 
        {
        if (shift===null)  shift = arr[i];
        else               setLast( lastPath, arr[i] );
        lastPath = path.join('-')
    } } }

  function setLast( last, val )
    {
    last.split('-')
    .reduce( (a,k,l,{[l+1]:n})=> 
      {
      if (n) return a[k];
      a[k] = val;
      }, arrXdim )
    }
  }
.as-console-wrapper {max-height: 100% !important;top: 0;}
.as-console-row::after {display: none !important;}

Mister Jojo0
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