CODEWITHSUNDEEP
javascript
Jack Evans
Jack Evans

Reputation: 43

Error in Javascript while trying to access element from array

I'm working on a MineSweeper program, and here's my problem:

So I make a 10x10 grid full of MineSquare objects which I defined earlier.

var grid = [];
    for (var i=0; i<10; i++){
        grid.push([]);
        for (var j=0; j<10; j++){
            grid[i].push(new MineSquare())
        }
    }

Then I make an array "bomb_list" to create 20 unique locations where the bombs will be. 

var bomb_list = [];
var found;
var rand;
while (bomb_list.length < 20){
    found = false;
    rand = Math.floor(Math.random() * 100);
    for (var i=0; i<bomb_list.length; i++){
        if (bomb_list[i] === rand){found=true; break;}
    }
    if(!found){
        bomb_list.push(rand);
    }
}

Then I try to change the value of those MineSquare's to indicate they are bombs.

for(var x in bomb_list){
    grid[ x / 10 ][ x % 10 ].touching = -1;
}

I am getting an error that says "Uncaught TypeError: Cannot read property '1' of undefined" which I believe is being caused when I try to take grid[x / 10].

Any reason why this is occuring?

Upvotes: 0

Views: 46

Answers (2)

vilsad
vilsad

Reputation: 76

X/10 will give you a float value, should use Math.ceil or Math.floor to get the nearest int as per your logic. Then it should work.

Upvotes: 1

Ivan
Ivan

Reputation: 10372

x/10 will produce a float. When x is 1, it will be 0.1. There is no index in grid of 0.1, so the result is undefined. That is why you get that error.

You can Math.floor or parseInt depending on what you are trying to do:

for(var x in bomb_list){
    grid[ parseInt(x / 10) ][ x % 10 ].touching = -1;
}

Upvotes: 1

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