HTML5 File API简单检查文件是否存在 [英] HTML5 File API simple check if file exists

问题描述

我有一个临时的文件API存储（HTML5），但我无法检查文件是否存在。有没有简单的方法来检查它？我是否必须实际尝试阅读该文件才能找到？

I have a temporary File API store (HTML5) but I can't check whether a file exists or not. Is there a simple way to check it? Do I have to actually try and read the file to find out?

搜索周围没有任何具体结果

A search around has yielded me nothing concrete

这可能是同步检查吗？

推荐答案

您必须阅读该文件。以下示例基于来自HTML5Rocks的此演示（它捕获所有错误，您可能想要过滤不同的错误类型）：

You have to read the file. The following example is based on this demo from HTML5Rocks (it catches all errors, you might want to filter the different error types):

    var errorHandler = function() {
        // File is not readable or does not exist!
    };
    fs.root.getFile('log.txt', {}, function(fileEntry) {
        fileEntry.file(function(file) {
            var reader = new FileReader();
            reader.onloadend = function() {
                // The file exists and is readable
            };
            reader.readAsText(file);
        }, errorHandler);
    }, errorHandler);

同步方法仅适用于Web Workers，因为它们具有阻塞性质。错误处理是略有不同。

The synchronous method is only available to Web Workers, due to their blocking nature. The error handling is slightly different.

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