使用JavaScript的FileReader接口时检测文件的内容类型

问题描述

我一直在为网络应用程序中的纯文本文件设置导入脚本。

I've been setting up an import script for plain-text files in a web application.

我的脚本如下：

function dataImport(files) {
    confirm("Are you sure you want to import the selected file? This will overwrite any data that is currently saved in the application workspace.");
    for (i = 0; i < files.length; i++) {
        file = files[i]
        console.log(file)
        var reader = new FileReader()
        ret = []
        reader.onload = function(e) {
            window.localStorage.setItem("ApplicationData", e.target.result);
        }
        reader.onerror = function(stuff) {
            console.log("error", stuff)
            console.log (stuff.getMessage())
        }
        reader.readAsText(file)
    }
}

它实质上是对的修改。

但是，目前用户可以在技术上尝试导入任何文件。因为它是为纯文本文件设计的，所以如果导入了不同类型的文件，就会出现问题。

However, at the moment the user can technically attempt to import any file. As it's designed for plain-text files, problems can arise if a different type of file is imported.

我在控制台中注意到浏览器检测到内容 - 要导入的文件的类型。这是一个例子。

I've noticed in the console that the browser detects the content-type of the file being imported. Here's an example.

fileName: "ideas.txt"
fileSize: 377
name: "ideas.txt"
size: 377
type: "text/plain"
webkitRelativePath: ""

那么，是否有可能设置一个参数，其中脚本检测到文件的内容类型，如果它不是许多指定的合适内容类型之一，则具有脚本拒绝导入吗？

Is it possible, then, to set up an argument where the script detects the content-type of the file, and if it isn't one of a number of specified suitable content-types, have the script refuse to import it?

提前感谢任何建议。

推荐答案

if (file.type.match('text/plain')) {
    // file type is text/plain
} else {
    // file type is not text/plain
}

String.match是一个RegEx ，所以如果你想检查，如果文件是任何类型的文本，你可以这样做：

String.match is a RegEx, so if you would want to check, if the file is any type of text, you could do that:

if (file.type.match('text.*')) {
    // file type starts with text
} else {
    // file type does not start with text
}

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