问题描述
文档：
为什么 FileList 一个对象而不是一个数组？它唯一的属性是 .length ，它唯一的方法是 .item（），这是多余的（ fileList [0] === fileList.item（0））。
Why is FileList an object rather than an array? The only property it has is .length and the only method it has is .item(), which is redundant (fileList[0] === fileList.item(0)).
推荐答案
嗯，可能有几个原因。首先，如果它是一个数组，你可以修改它。您无法修改 FileList 实例。其次但是相关的，它可能（可能是）浏览器数据结构的视图，因此最小的功能集使实现更容易提供它。
Well, there could be several reasons. For one, if it were an array, you could modify it. You can't modify a FileList instance. Secondly but related, it could be (probably is) a view onto a browser data structure, so a minimal set of capabilities makes it easier for implementations to provide it.
2018年更新：有趣的是，有一个关于 FileList 的注释：
Update in 2018: Interestingly, though, the spec has a note on FileList:
（我觉得很奇怪，我认为趋势是朝向可迭代，而不是数组 —例如更新将其标记为 iterable ，以便与扩展语法兼容， for-of 和 forEach 。）
(Which I find odd, I thought the trend was toward iterable, not Array — such as the update to NodeList marking it iterable for compatibility with spread syntax, for-of, and forEach.)
您还可以将其转换为一个数组通过 Array.from（theFileList）。
You can also convert it to an array via Array.from(theFileList).
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