如何從對象函數返回一個對象 - javascript？

Question

我有一個像下面

function obj() { 

    this.cellSize = 50; 

    this.createBlock = function() { // creates a block object 
     this.x = 0; 
     this.y = 0 - (this.cellSize * 1.5); 
     this.baseVelocity = 1; 
     this.velocity = this.baseVelocity; 
     return this; 
    }; 

    this.activeBlock = this.createBlock(); // active block object 

    this.nextBlock = this.createBlock(); // next block object 
} 

對象當我檢查obj.activeBlock我沒有得到應該從obj.createBlock返回的對象？

感謝，

Answer 1

你可能想是這樣的：

function obj() { 
    var that = this; 
    this.cellSize = 50; 

    this.createBlock = function() { // creates a block object 
     this.x = 0; 
     this.y = 0 - (that.cellSize * 1.5); 
     this.baseVelocity = 1; 
     this.velocity = this.baseVelocity; 
     return this; 
    }; 

    this.activeBlock = new this.createBlock(); // active block object 

    this.nextBlock = new this.createBlock(); // next block object 
} 

的this在createBlock功能應該從obj()的this不同。您還需要爲每個塊使用new創建一個新對象。如果cellSize應該是一個常量，則可以將代碼重寫爲閉包：

function obj() { 
    var cellSize = 50; 

    this.createBlock = function() { // creates a block object 
     this.x = 0; 
     this.y = 0 - (cellSize * 1.5); 
     this.baseVelocity = 1; 
     this.velocity = this.baseVelocity; 
     return this; 
    }; 

    this.activeBlock = new this.createBlock(); // active block object 

    this.nextBlock = new this.createBlock(); // next block object 
}