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:45Please respect copyright.ＰＥＮＡＮＡkHbYWVQbNm
---read whole file content into array buffer---45Please respect copyright.ＰＥＮＡＮＡZ9ngSON0Y3
let file=input.files[0]; const reader = new FileReader(); 45Please respect copyright.ＰＥＮＡＮＡEctOKkNExP
reader.onload = () => 45Please respect copyright.ＰＥＮＡＮＡXL7VCVQ9Fv
{45Please respect copyright.ＰＥＮＡＮＡnjG3k5IxGg
let content_whole = new Uint8Array(reader.result);45Please respect copyright.ＰＥＮＡＮＡbojql107l8
}45Please respect copyright.ＰＥＮＡＮＡBTxX30xPLD
reader.readAsArrayBuffer(file);45Please respect copyright.ＰＥＮＡＮＡvWPWH6gvzS
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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:45Please respect copyright.ＰＥＮＡＮＡ7dYwUZ6q14
---read part of file content into array buffer---45Please respect copyright.ＰＥＮＡＮＡX4fTG803GU
let file=input.files[0], block_size=1000000, start=0, end=block_size; const reader = new FileReader(); 45Please respect copyright.ＰＥＮＡＮＡfVxSGJjTX7
reader.onload = () => 45Please respect copyright.ＰＥＮＡＮＡTXhNSquGGY
{45Please respect copyright.ＰＥＮＡＮＡpQRM1rDt1K
let content_part = new Uint8Array(reader.result);45Please respect copyright.ＰＥＮＡＮＡM85trxX2iZ
}45Please respect copyright.ＰＥＮＡＮＡtXCsrMMOqR
reader.readAsArrayBuffer(file.slice(start,end));45Please respect copyright.ＰＥＮＡＮＡtj8DXWHUef
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45Please respect copyright.ＰＥＮＡＮＡkvwIvFLGjg
Section X. Thanks45Please respect copyright.ＰＥＮＡＮＡ80GLe7ICji
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.com45Please respect copyright.ＰＥＮＡＮＡfhwRq8ibpF
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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