var mouseState = false;
var toSelected = false;

$(".cell").on("mousedown", function() (
    mouseState = true;
    console.log(mouseState);
    (this).toggleClass("selected");
    toSelected = (this).hasClass("selected");
)).on("mouseup", function() (
    mouseState = false;
    console.log(mouseState);
)).on("mouseenter", function() (
    if (mouseState) (
        if (toSelected) {
            (this).addClass("selected");
        } else {
            (this).removeClass("selected");
        }
    );
));