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function rotateImage(arr) {
    
    // rotates a 2D array 90 degrees to the right (clockwise)

	var newarr = [];

	for(let x = 0; x < arr[0].length; x++){
	  newarr[x] = [];
	  for(let y = arr.length - 1; y >= 0; y--){
	    newarr[x].push( arr[y][x] );
	  }
	}

	return newarr;
  
}

console.log(rotateImage([[1,2,3], 
                         [4,5,6], 
                         [7,8,9]]));