本文描述了使用javascript读取用户通过Input控件选择的文件的内容的方法和注意事项。后面用英文写，但我的英文不太好，如有错误之处，希望大家帮我纠正，我的联系方式在后面。
When user select a file by <input type=file>, its content can be read by javascript like this:175Please respect copyright.ＰＥＮＡＮＡ334nadrqzX
---read whole file content into array buffer---175Please respect copyright.ＰＥＮＡＮＡXCrWufCABC
let file=input.files[0]; const reader = new FileReader(); 175Please respect copyright.ＰＥＮＡＮＡWNYE8kZ4w6
reader.onload = () => 175Please respect copyright.ＰＥＮＡＮＡi0SGzzvF27
{175Please respect copyright.ＰＥＮＡＮＡUzTsSjRPJz
let content_whole = new Uint8Array(reader.result);175Please respect copyright.ＰＥＮＡＮＡS1eJZuHRYI
}175Please respect copyright.ＰＥＮＡＮＡeir7nPnvHE
reader.readAsArrayBuffer(file);175Please respect copyright.ＰＥＮＡＮＡFnnH0RlaO3
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If the file size is too large, the browser may crash as the whole file content are loaded into memory by array buffer. In order to avoid it, we can just read a part of the file like this:175Please respect copyright.ＰＥＮＡＮＡcAXb4I0EgQ
---read part of file content into array buffer---175Please respect copyright.ＰＥＮＡＮＡBBhrj1ZVGd
let file=input.files[0], block_size=1000000, start=0, end=block_size; const reader = new FileReader(); 175Please respect copyright.ＰＥＮＡＮＡDxbzkEts5x
reader.onload = () => 175Please respect copyright.ＰＥＮＡＮＡBBBQEmKSNT
{175Please respect copyright.ＰＥＮＡＮＡg4TwXN6jyW
let content_part = new Uint8Array(reader.result);175Please respect copyright.ＰＥＮＡＮＡYOxOyfyyCo
}175Please respect copyright.ＰＥＮＡＮＡr4L9hGmHDl
reader.readAsArrayBuffer(file.slice(start,end));175Please respect copyright.ＰＥＮＡＮＡgt23Xd9f3B
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175Please respect copyright.ＰＥＮＡＮＡJz5j1eRJt8
Section X. Thanks175Please respect copyright.ＰＥＮＡＮＡN8DjrVrzGF
https://segmentfault.com/a/1190000022113605
Section Y. Contacts Me
If you found any errors or have any suggestions for this article, please let me know, my wechat: si_jinmin, my email: [email protected]175Please respect copyright.ＰＥＮＡＮＡh5cvFvjY30
如果您发现本文有任何错误，或者对本文有好的建议，欢迎与我联系探讨，我的微信: si_jinmin, 我的email: [email protected]
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