code not reached after for loop (javascript)

Question

In this function, right after the first for loop, code isn't being reached. The alert("can't get here"); isn't working. Am I missing some obvious JavaScript caveat here? The rest of the code can be found here: http://jsbin.com/tiweniludoqe/7/edit Any help is much appreciated.

function checkForWin(){

    var winCondition = 0;

    //check for horizontal wins
    for(i = 0; i < board[i].length; i++) {
        for(j = 0; j < board[i].length; j++) {
            winCondition += board[i][j];
            if(winCondition === board[i].length) {
                alert("win detected horizontal");
            }
        }
        winCondition = 0;
    }
    alert("can't get here");

    //check for vertical wins
    for(i = 0; i < board[i].length; i++) {
        for(j = 0; j < board[i].length; j++) {
            winCondition += board[j][i];
            alert("winCondition: " + winCondition);
            if(winCondition === board[i].length) {
                alert("win detected horizontal");
            }
        }
    }

    //if diagonal / is 3 or -3 win
    //if diagonal \ is 3 or -3 win
}

Do you see any errors in your console? Edit: There is an uncaught error: Cannot read property 'length' of undefined — Jack
– Jack, Commented Sep 14, 2014 at 22:47
well your first loop condition should be board.length instead of board[i].length — LJᛃ
– LJᛃ, Commented Sep 14, 2014 at 22:48
Isn't board[i] an array as well though? That is, an array inside an array. — Van
– Van, Commented Sep 14, 2014 at 22:52
Declare i and j with var and use console.log() instead of alert() — Pointy
– Pointy, Commented Sep 14, 2014 at 22:56

Augusto Altman Quaranta · Accepted Answer · 2014-09-14 23:02:08Z

I think that your code is falling into an infinite loop by checking for board[i].length in the first for loop.

Try this:

function checkForWin(){

    var winCondition = 0;

    //check for horizontal wins
    for(i = 0; i < board.length; i++) { //HERE WE CHECK FOR board.length INSTEAD OF board[i].length
        for(j = 0; j < board[i].length; j++) {
            winCondition += board[i][j];
            if(winCondition === board[i].length) {
                alert("win detected horizontal");
            }
        }
        winCondition = 0;
    }
    alert("can't get here");

    //check for vertical wins
    for(i = 0; i < board.length; i++) { //HERE YOU HAD THE SAME PROBLEM
        for(j = 0; j < board[i].length; j++) {
            winCondition += board[j][i];
            alert("winCondition: " + winCondition);
            if(winCondition === board[i].length) {
                alert("win detected horizontal");
            }
        }
    }

    //if diagonal / is 3 or -3 win
    //if diagonal \ is 3 or -3 win
}

Final recomendation... When iterating with for loops try to user the var for the iterating variable, like this:

for(var i=0; i < board.length; i++)

Instead of:

for(i=0; i < board.length; i++)

By doing this you are avoiding to populate the global scope with those variables (in the case above i).

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