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:172Please respect copyright.ＰＥＮＡＮＡYHnAre8xjC
---read whole file content into array buffer---172Please respect copyright.ＰＥＮＡＮＡz5b3D3xa2V
let file=input.files[0]; const reader = new FileReader(); 172Please respect copyright.ＰＥＮＡＮＡmoar5tEBcB
reader.onload = () => 172Please respect copyright.ＰＥＮＡＮＡgMmf2fZjLy
{172Please respect copyright.ＰＥＮＡＮＡI2cucSeLjC
let content_whole = new Uint8Array(reader.result);172Please respect copyright.ＰＥＮＡＮＡdynDFtCLpH
}172Please respect copyright.ＰＥＮＡＮＡU03zJmglMC
reader.readAsArrayBuffer(file);172Please respect copyright.ＰＥＮＡＮＡdczpe9FBe7
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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:172Please respect copyright.ＰＥＮＡＮＡHqwfBq8kz1
---read part of file content into array buffer---172Please respect copyright.ＰＥＮＡＮＡdRAgJxNM2H
let file=input.files[0], block_size=1000000, start=0, end=block_size; const reader = new FileReader(); 172Please respect copyright.ＰＥＮＡＮＡZJCFuihaG0
reader.onload = () => 172Please respect copyright.ＰＥＮＡＮＡOiYY30pYJb
{172Please respect copyright.ＰＥＮＡＮＡ3xrKZOEF84
let content_part = new Uint8Array(reader.result);172Please respect copyright.ＰＥＮＡＮＡ6PXB5YCEd1
}172Please respect copyright.ＰＥＮＡＮＡSsCp047QVP
reader.readAsArrayBuffer(file.slice(start,end));172Please respect copyright.ＰＥＮＡＮＡXqmf9BKEfI
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172Please respect copyright.ＰＥＮＡＮＡjEqylEUygV
Section X. Thanks172Please respect copyright.ＰＥＮＡＮＡxrToDdp3Ch
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]172Please respect copyright.ＰＥＮＡＮＡwv6UgPHOxT
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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