this._waiting is undefined

Question

我想爲web工作者編寫一個簡單的包裝類。當其中一個定義的消息發送給webworker時，LayoutBridge會分配一個票據，該票據在處理請求時返回。這樣，我應該可以爲這些請求運行回調。

我收到以下錯誤

TypeError: this._waiting is undefined

在_recvMsg。

下面是代碼，我一直試圖解決這個自制謎語幾天，但無法看到我做錯了什麼，因爲等待在LayoutBridge構造函數和（只是以確保）在init函數中。

我會在此之後立即發佈的jsfiddle，但也許有人知道答案了。

var LayoutBridge = function(){ 

    this._waiting = {}; 
    this._initialized = false; 

}; 

LayoutBridge.prototype.init = function(opts){ 
    if(!this._initialized){ 
     this._waiting = {}; 

     this._worker = new Worker('/layout-worker.js'); 
     this._worker.onmessage = this._recvMsg; 
     var ticket = _.uniqueId(); 

     var waitingCallback = function(){ 
      this._initiated = true; 
     }; 
     waitingCallback.bind(this); 
     this._waiting[ticket] = waitingCallback; 

     this._worker.postMessage({cmd: 'init', ticket: ticket}); 
     this._initialized = true; 
    } 
}; 

LayoutBridge.prototype.addVertex = function(callback){ 
    if(!this._initialized) throw "Initialize LayoutBridge first"; 

    var ticket = _.uniqueId(); 
    this._waiting[ticket] = callback; 
    this._worker.postMessage({cmd: 'addVertex', ticket: ticket}); 
}; 

LayoutBridge.prototype.removeVertex = function(id, callback){ 
    if(!this._initialized) throw "Initialize LayoutBridge first"; 

    var ticket = _.uniqueId(); 
    this._waiting[ticket] = callback; 
    this._worker.postMessage({cmd: 'removeVertex', id: id, ticket: ticket}); 
}; 

LayoutBridge.prototype.addEdge = function(sourceId, targetId, callback){ 
    if(!this._initialized) throw "Initialize LayoutBridge first"; 

    var ticket = _.uniqueId(); 
    this._waiting[ticket] = callback; 
    this._worker.postMessage({cmd: 'addEdge', sourceId: sourceId, targetId: targetId}); 
}; 

LayoutBridge.prototype._recvMsg = function(e){ 
    this._waiting[e.data.ticket](e.data.payload); 
    //delete this._waiting[e.data.ticket]; 
}; 

編輯，這裏的小提琴：包括建議：http://jsfiddle.net/MGSvj/2/

Answer 1

分配你的函數到另一個階級改變其範圍。

這裏你指定你的this._recvMsg功能Worker類。

this._worker.onmessage = this._recvMsg; 

因此，在這裏的代碼，這將是本機窗口對象或工人對象（也不太清楚這件事，但它絕對不會是LayoutBridge對象）。

LayoutBridge.prototype._recvMsg = function(e){ 
    this._waiting[e.data.ticket](e.data.payload); 
    //delete this._waiting[e.data.ticket]; 
}; 

爲了解決這個問題，所有你需要做的是

var oThis = this; 
this._worker.onmessage = function(){ oThis._recvMsg }; 

而且，按照https://developer.mozilla.org/en/docs/DOM/Blob

斑點需要數組作爲參數。

所以，你的代碼

var blob = new Blob($('#layout-worker').html()); 

應該

var blob = new Blob([$('#layout-worker').html()]);