Eloquent JavaScript chessboard

Question

Is this a good way to solve the quiz "Chessboard" from http://eloquentjavascript.net/02_program_structure.html ?

Write a program that creates a string that represents an ×ばつ8 grid, using newline characters to separate lines. At each position of the grid there is either a space or a "#" character. The characters should form a chess board.

When you have a program that generates this pattern, define a variable size = 8 and change the program so that it works for any size, outputting a grid of the given width and height.

This is my code:

 size = 10; 
 
 grid = ""
 
 for (var i = 1; i <= size; i++) {
 for (var j = 1; j <= size; j++) {
 if (i % 2 === 0) {
 	grid+= "# "
 } else {
 	grid+= " #"
 }
 }
 grid+= "\n"
 }
 
 
 console.log(grid)

• DFord: You put a '#' and a space in each 'cell'. The problem you posted says space OR '#'. So for each iteration of the inner loop, it should be grid += "#"; or grid += " ";
• 200_success: This code produces a board that is larger than the size specified in the challenge.

Answer 1

Fun question;

• you should write a function that takes a parameter instead of just writing the code

• A chessboard has lots of repetition, take a minute to ponder how String.repeat could make this code much simpler.

• Your indentation is not perfect, consider using a site like http://jsbeautifier.org/

• I am not a big fan of var within the loop, I would declare var up front.

This is a possible solution that provides the right size of the board:

function createChessboardString(size){
 const line = ' #'.repeat( size ),
 even = line.substring(0,size),
 odd = line.substring(1,size+1);
 let out = '';
 while(size--){
 out = out + ((size % 2) ? odd: even ) + '\n';
 }
 return out;
}
console.log(createChessboardString(8));

You could consider for very large boards that the board in essence repeats odd + '\n' + even, so you could repeat that as well. The problem for me is that there are too many corner cases to consider. So personally I would go for the above for any board size < 1000.

• olivier: one question: I changed the code to (i + j) % 2 === 0 because i took a look in the solution. Could you please explain me this? Why adding these together? @konijn
• konijn: I would have to see the surrounding code, plus that is not really what codereview is about. I was just thinking that your code seems wrong actually. If ' ' is white and '#'' is black, then your board is way too big.
• Radmation: @konijn why are you not a fan of var within the loop?
• konijn: Cant find back the exact location, but it's in there: github.com/airbnb/javascript#variables basically js hoists those variables anyway to the top
• Roland Illig: Your codeuses very incon sistentspacing.