Question on Randy Hoyt's Robot Maze

Question

Hi team Treehouse!
Firstly, let me tell you that I LOVED Randy's workshop. Just going through a program from start to finish has done WONDERS in helping me understand how to think about program design. Please keep workshops coming!
I have one question that has been bugging me. It is when Randy creates spaces on his Maze object. Here is the code:
```javascript
this.directions = ["north", "east", "south", "west"];
    this.spaces = [];
    var x, y; 
        //for loop goes through each column, creating an array for it
    for (x=1; x<=width; x+=1) {
        this.spaces[x] = []; //In each column create empty array
        for (y=1; y<=height; y+=1) { //add one element to array for each space in column
        this.spaces[x][y] = new MazeSpace(this.directions);
        };
    };
};
```
I have no clue how/what this.spaces[x][y] is creating the array within the arrays. Can you point me to some documentation that explains this syntax (i.e. property[array1][array2]). I would love to know not just THAT this works, but how.
He uses a similar syntax in his canMove function on the Robot object:
javscript
if (this.spaces[forwardX][forwardY][opposites[direction]]) {
        return false; //checks to see if there is a wall on the forward space
    };

Thanks!

Dave McFarland · Answer

Hi,
You use this kind of syntax -- items[0][1] -- when have nested arrays. That is, an array that is itself an element in an array:

var items = [
  [1, 2],
  [3, 4],
  [5, 6]
];

Each element in the items array above is itself an array. So items[0] is [1,2]. If you want to access number 3 above, you need to access the second element in the items array, and the first element in that array like this: items[1][0].

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Spencer Christensen

Spencer Christensen

Question on Randy Hoyt's Robot Maze

1 Answer

Dave McFarland

Dave McFarland