JavaScript - Transpose a 2D array

transpose.js

/**
 * Transpose an array of arrays using matrix transposition.
 * The array is returned, *NOT* transposed in place.
 * 
 * Handles matrixes where the number of rows != number of columns.
 * The number of columns in each row must be the same.
 * E.g.
   [            |    [            
    [1,2,3],    |     [1,2],    
    [4,5,6],    |     [3,4],    
    [7,8,9],    |     [5,6],    
   ]            |    ]            
   becomes      |    becomes      
   [            |    [            
    [1,4,7],    |     [1,3,5],    
    [2,5,8],    |     [2,4,6],
    [3,6,9],    |    ]     
   ]            |                
 * @param  {Array} array The array to transpose.
 * @return {Array}
 */
function transpose( array ) {
  let newArray = [];

  for (let i = 0, len = array[0].length; i < len; i++) {
    newArray.push( [] );
    for (let j = 0, len = array.length; j < len; j++) {
      newArray[i].push( array[j][i] );
    }
  }

  return newArray;
}