JavaScript 代码在回调中不起作用

Question

在以下 JavaScript 代码中，如果 warnBeforeNew 为 false，则文件打开代码有效。但是，如果 warnBeforeNew 为 true，则不会，而是给出错误“Uncaught TypeError:无法读取未定义的属性“root””。

我不知道这是否与范围有关，但是如何让文件加载代码在回调中工作？谢谢。

Editor.prototype.open = function(path) {
  if (Editor.warnBeforeNew==true){
    this.showDialog({
        dialogLabel: 'You have unsaved changes. Are you sure you want to discard them and open a different file?',
        submitLabel: 'Discard',
        cancelLabel: 'Cancel',
        submitCallback: function() {
          Editor.warnBeforeNew=false;
          this.filesystem.root.getFile(path, {}, this.load.bind(this), error.bind(null, "getFile " + path));
        }
    });
  } else {
    this.filesystem.root.getFile(path, {}, this.load.bind(this), error.bind(null, "getFile " + path));
  }
};

Answer 1

您必须保存 this 的值，因为调用回调时，它使用与外部函数不同的接收器:

if (Editor.warnBeforeNew==true){
    var thing = this; // choose a more meaningful name if possible...
    this.showDialog({
        dialogLabel: 'You have unsaved changes. Are you sure you want to discard them and open a different file?',
        submitLabel: 'Discard',
        cancelLabel: 'Cancel',
        submitCallback: function() {
          Editor.warnBeforeNew=false;
          thing.filesystem.root.getFile(path, {}, thing.load.bind(thing), error.bind(null, "getFile " + path));
        }
    });
  } else {
    this.filesystem.root.getFile(path, {}, this.load.bind(this), error.bind(null, "getFile " + path));
  }