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.ＰＥＮＡＮＡUZ8CqXLinw
---read whole file content into array buffer---175Please respect copyright.ＰＥＮＡＮＡYPHEJbhjLg
let file=input.files[0]; const reader = new FileReader(); 175Please respect copyright.ＰＥＮＡＮＡFBgDJW584Q
reader.onload = () => 175Please respect copyright.ＰＥＮＡＮＡXrFuplOK46
{175Please respect copyright.ＰＥＮＡＮＡ04Dxbn8BCN
let content_whole = new Uint8Array(reader.result);175Please respect copyright.ＰＥＮＡＮＡfDpPdt7npS
}175Please respect copyright.ＰＥＮＡＮＡQ7agyyJ8H8
reader.readAsArrayBuffer(file);175Please respect copyright.ＰＥＮＡＮＡ4WjqGFor3P
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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.ＰＥＮＡＮＡPxFj97hw70
---read part of file content into array buffer---175Please respect copyright.ＰＥＮＡＮＡeT2LzAJc3W
let file=input.files[0], block_size=1000000, start=0, end=block_size; const reader = new FileReader(); 175Please respect copyright.ＰＥＮＡＮＡZ9egUu9J8b
reader.onload = () => 175Please respect copyright.ＰＥＮＡＮＡVC7XRjNp70
{175Please respect copyright.ＰＥＮＡＮＡ7a0B0KQsJb
let content_part = new Uint8Array(reader.result);175Please respect copyright.ＰＥＮＡＮＡZX4vn88J6S
}175Please respect copyright.ＰＥＮＡＮＡfP2nToHxHR
reader.readAsArrayBuffer(file.slice(start,end));175Please respect copyright.ＰＥＮＡＮＡnzVAbKXuuQ
-----------------------------------------------
175Please respect copyright.ＰＥＮＡＮＡyjdZeP41vw
Section X. Thanks175Please respect copyright.ＰＥＮＡＮＡw6ODWd6s5V
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.com175Please respect copyright.ＰＥＮＡＮＡaOUXXB4b32
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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