this.someprop在构造函数中是未定义的？

Question

这是我的代码：

var PLAYER_INIT_ROW = 6;
var PLAYER_INIT_COL = 3;

var Player  = function(){
    this.sprite = 'images/char-boy.png';
    var row = PLAYER_INIT_ROW;
    var col = PLAYER_INIT_COL;

    log("row:"+row);
    log("this.row:"+this.row);
    log("this:"+this);

    var coord = getCoord(row,col);
    var x = coord.x;
    var y = coord.y;

};

var player = new Player();

和日志：

row:  6
this.row:  undefined
this:  [object Object]

和chrome调试器：

Local
col:3
coord:undefined
row:6
this:Player
    sprite:"images/char-boy.png"
    __proto__:Object
x:undefined
y:undefined

所以，'this'存在但是this.row未定义。我猜当构建完成时，this.row将被定义，不是吗？