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:48Please respect copyright.ＰＥＮＡＮＡNbRdkseAr9
---read whole file content into array buffer---48Please respect copyright.ＰＥＮＡＮＡsEUQGuTtWf
let file=input.files[0]; const reader = new FileReader(); 48Please respect copyright.ＰＥＮＡＮＡKnnuNyzo8d
reader.onload = () => 48Please respect copyright.ＰＥＮＡＮＡljSLyAIBcb
{48Please respect copyright.ＰＥＮＡＮＡzwBqKyPt5N
let content_whole = new Uint8Array(reader.result);48Please respect copyright.ＰＥＮＡＮＡceHIgp5kGP
}48Please respect copyright.ＰＥＮＡＮＡUD1VBTsWsI
reader.readAsArrayBuffer(file);48Please respect copyright.ＰＥＮＡＮＡeFNx3oDIMb
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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:48Please respect copyright.ＰＥＮＡＮＡBG4JhbpTaY
---read part of file content into array buffer---48Please respect copyright.ＰＥＮＡＮＡbf5WYWuI1A
let file=input.files[0], block_size=1000000, start=0, end=block_size; const reader = new FileReader(); 48Please respect copyright.ＰＥＮＡＮＡvxrZDSkE0X
reader.onload = () => 48Please respect copyright.ＰＥＮＡＮＡ4PiQQ9Oqrm
{48Please respect copyright.ＰＥＮＡＮＡJ8o830xT93
let content_part = new Uint8Array(reader.result);48Please respect copyright.ＰＥＮＡＮＡwQZhOQT8VL
}48Please respect copyright.ＰＥＮＡＮＡmmGJnWikZZ
reader.readAsArrayBuffer(file.slice(start,end));48Please respect copyright.ＰＥＮＡＮＡWGtB3uYJq9
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48Please respect copyright.ＰＥＮＡＮＡzjbppWpAlW
Section X. Thanks48Please respect copyright.ＰＥＮＡＮＡfYsf8ivceW
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: si.jinmin@gmail.com48Please respect copyright.ＰＥＮＡＮＡ8MDQpTRoir
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: si.jinmin@gmail.com
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