将参数传递给FileReader onload事件 [英] Pass a parameter to FileReader onload event

问题描述

我需要阅读一些由用户提供的csv文件。使用拖放div将文件传递给页面/脚本，处理文件放置如下：

I need to read some csv files, given by the user. Files are passed to the page/script using a drag and drop div, that handles the file drop as follows:

function handleFileDrop(evt) {
    evt.stopPropagation();
    evt.preventDefault();
    var files = evt.dataTransfer.files; // FileList object.
    ...
}

我需要用csv解析每个文件库，它将其转换为一个数组，但我也需要跟踪我目前解析的文件名。下面是我用来解析每个文件的代码：

I need to parse each file with a csv library that converts it into an array, but I also need to keep track of the file name I'm currently parsing. Here's the code I use to parse each file:

for(var x = 0; x < files.length; x++){
    var currFile = files[x];
    var fileName = currFile.name;
    var reader = new FileReader();
    reader.onload = (function(theFile){
        return function(e){
            var csvArr = CSV.csvToArray( e.target.result, ";", true );
            console.log(csvArr); 
        };
    })(currFile);   
    reader.readAsText(currFile);
}

在此之前，一切都很好。我需要的是将文件名传递给 reader.onload 事件，例如：

Until this, everything works great. What I need is to also pass the filename to the reader.onload event, eg:

reader.onload = (function(theFile){
    return function(e){

       ***** I need to have fileName value HERE *****

    };
})(currFile); 

有可能吗？我怎样才能做到这一点？感谢您的任何帮助，最好的问候

Is possible? How can I do this? Thanks in advance for any help, best regards

推荐答案

请尝试以下操作：

Try the following:

var reader = new FileReader();
reader.onload = (function(theFile){
    var fileName = theFile.name;
    return function(e){
        console.log(fileName);
        console.log(e.target.result);
    };
})(currFile);   
reader.readAsText(currFile);

在这里，您要创建一个新的 fileName 每次将文件传递给外部方法时都会变量。然后创建一个访问该变量的函数（由于关闭）并返回它。

Here, you're creating a new fileName variable each time a file is passed to the outer method. You're then creating a function which has access that variable (due to the closure) and returning it.

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