JS属性作为同一对象的方法的返回值

Question

Edited to include more info about what I'm trying to achieve.

The code below works fine, but when I uncomment the boardGen:.. and board:.. sections to make board of flexible size, no board is created, or it's of 0 dimensions (no error). Could someone please explain why, and tell me how to make it work properly?

$(document).ready(function () {

    var app = {

        // define inital matrix
        // to do: build helper function to make arbitary size grid
        board : [[0, 0, 0, 0, 0],
        [0, 0, 0, 0, 0],
        [0, 0, 0, 0, 0],
        [0, 0, 0, 0, 0],
        [0, 0, 0, 0, 0]],

        // boardGen : function (rows, cols) {
            // var array = [],
            // row = [];
            // while (cols--)
                // row.push(0);
            // while (rows--)
                // array.push(row.slice());
            // return array;
        // },

        // board : function () {
            // return app.boardGen(6, 6);
        // },

        init : function () {
            // on startup
            app.createCells();
            app.main();
        },

        createCells : function () {
            // create cells and populate
            var html = '<table>';
            for (var i = 0, len = app.board.length; i < len; ++i) {
                html += '<tr>';
                for (var j = 0, rowLen = app.board[i].length; j < rowLen; ++j) {
                    html += `<td class="cell" data-gridpos="[${i}, ${j}]">`;
                    html += `${app.board[i][j]}</td>`;
                }
                html += "</tr>";
            }
            html += '</table>';
            $('#instructions').after(html);
        },

        numNeighbours : function (arr, coords) {
            var row = coords[0];
            var col = coords[1];
            var neighbours = 8;
            var offsets = [[-1, -1], [-1, 0], [-1, 1], [0, -1], [0, 1], [1, -1], [1, 0], [1, 1]];
            for (offset of offsets) {
                // prevent errors for non-existant indices
                try {
                    neighbour = arr[row + offset[0]][col + offset[1]];
                } catch (err) {
                    neighbour = undefined;
                }
                if (!neighbour) {
                    neighbours--;
                }
            }
            return neighbours;
        },

        main : function () {
            var coords = [];
            $(document).on('click', '.cell', function () {
                // get data for current cell
                coords = $(this).data('gridpos');
                // highlight current cell
                $(this).css('background-color', 'lightgray');
                $('td').not(this).css('background-color', '');
                // update info re neighbours
                $('#info').html('Touching: ' + app.numNeighbours(app.board, coords));
                // console.log(app.numNeighbours(coords));
                // toggle values in cells and update board
                if (app.board[coords[0]][coords[1]] == 1) {
                    app.board[coords[0]][coords[1]] = 0;
                    $(this).html('0')
                } else {
                    app.board[coords[0]][coords[1]] = 1;
                    $(this).html('1')
                }
            });
        }
    };
    app.init();
});

Answer 1

1. The object literal gets evaluated
2. An object is created
3. The object is assigned to app

You can't read the value of app during step 1, since it doesn't have a value until step 3.