Angular2 + Typescript + FileReader.onLoad =属性不存在 [英] Angular2 + Typescript + FileReader.onLoad = property does not exist

问题描述

我正在使用 FileReader接口并使用异步方法 readAsText（）来读取本地文本文件，
之后 onload事件被调用，我尝试读取我的文件，我的源代码如下：

  export class ReadFileComponent {
 text：string; 
 
 readFile（）：void {
 let reader = new FileReader（）; 
 reader.onload = function（e）{
 this.text = reader.result; 
} 
 reader.readAsText（file）; 
} 
} 
  

编译失败，因为Property text 类型FileReader b

我认为这是由于EventListener接口不接受对象， p>

有人请解决这类问题吗？

谢谢你们，

解决方案

如果你想在回调中使用这个，请使用箭头功能，否则它将无效

  reader.onload =（e）=> {
 this.text = reader.result; 
} 
  

https://developer.mozilla.org/en/docs/Web/JavaScript/Reference/Functions/Arrow_functions

I am using the FileReader Interface and it’s asynchronous method readAsText() to read a local text file, After that when the onload event is called, I try to read my file, my source code is something like the following:

export class ReadFileComponent {
   text: string;

   readFile(): void {
     let reader=new FileReader();
     reader.onload = function(e) {
        this.text=reader.result;
     }
     reader.readAsText(file);   
   }
}

compilation is failed because Property "text" does not exist on type "FileReader"

I think this is due to the EventListener interface does not accept objects ,

did someone please solve this kind of issue?

thanks guys,

解决方案

If you want to use this inside the callback, use an arrow function, otherwise it won't work

reader.onload = (e) => {
    this.text=reader.result;
}

https://developer.mozilla.org/en/docs/Web/JavaScript/Reference/Functions/Arrow_functions

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