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:173Please respect copyright.ＰＥＮＡＮＡ82la7fwmD6
---read whole file content into array buffer---173Please respect copyright.ＰＥＮＡＮＡ81o1YYsDaR
let file=input.files[0]; const reader = new FileReader(); 173Please respect copyright.ＰＥＮＡＮＡDIZz9aTupY
reader.onload = () => 173Please respect copyright.ＰＥＮＡＮＡq2ROIUgfzE
{173Please respect copyright.ＰＥＮＡＮＡYi3MIzEFic
let content_whole = new Uint8Array(reader.result);173Please respect copyright.ＰＥＮＡＮＡKiijze7Nm6
}173Please respect copyright.ＰＥＮＡＮＡUwpVZqD3bm
reader.readAsArrayBuffer(file);173Please respect copyright.ＰＥＮＡＮＡGPb6Ccm2hi
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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:173Please respect copyright.ＰＥＮＡＮＡTAgxJYi4G8
---read part of file content into array buffer---173Please respect copyright.ＰＥＮＡＮＡqo6behgJOe
let file=input.files[0], block_size=1000000, start=0, end=block_size; const reader = new FileReader(); 173Please respect copyright.ＰＥＮＡＮＡD0HXU2XvKv
reader.onload = () => 173Please respect copyright.ＰＥＮＡＮＡy6FzDnrKxx
{173Please respect copyright.ＰＥＮＡＮＡlV7b5G9R3f
let content_part = new Uint8Array(reader.result);173Please respect copyright.ＰＥＮＡＮＡjr60fmKWXn
}173Please respect copyright.ＰＥＮＡＮＡwg6CpwC6FI
reader.readAsArrayBuffer(file.slice(start,end));173Please respect copyright.ＰＥＮＡＮＡInHoyiDUrp
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173Please respect copyright.ＰＥＮＡＮＡ3S0qW6BPvr
Section X. Thanks173Please respect copyright.ＰＥＮＡＮＡhizLG4oOu8
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]173Please respect copyright.ＰＥＮＡＮＡ4BjBmFMWqo
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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