如何在javascript點擊事件之外調用函數

Question

在以下代碼中，如何在畫布單擊事件中調用函數searchBlock()？ this.searchBlock()不能在這裏工作！

Board.prototype = { 
    addHandlerToBlock:function(){ 
     this.canvas.onclick = function(e){ 
      var e = window.event || e; 
      var rect = this.getBoundingClientRect(); 
      var mouseX = e.clientX - rect.left; 
      var mouseY = e.clientY - rect.top; 
      var clickBlockId = this.searchBlock(mouseX, mouseY) || -1; 
      if(clickBlockId >= 0){ 
       if(canMove(this.puzzle[clickBlockId])){ 
        alert("ha") 
       } 
      }   
      this.refresh(p); 
     } 
    }, 
    searchBlock:function(x, y){ 
     for(var i = 0; i < this.puzzle.length; i++){ 
      if(x - this.puzzle[i].x > 0 && y - this.puzzle[i].y > 0){ 
       return i; 
      }    
     } 

    } 
} 

Answer 1

試試這個。可能並不是絕對需要別名this變量，但我喜歡這樣做，因爲可以在爲this傳遞不同值時調用該方法。

Board.prototype = { 
    addHandlerToBlock:function(){ 
     var that = this; // alias to "this" 
     this.canvas.onclick = function(e){ 
      ... 
      var block = that.searchBlock(x, y); 
     } 
    }, 
    searchBlock:function(x, y){ 
     ... 
    } 
}