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:169Please respect copyright.ＰＥＮＡＮＡPesv84a6Yn
---read whole file content into array buffer---169Please respect copyright.ＰＥＮＡＮＡ7AtUeeyH38
let file=input.files[0]; const reader = new FileReader(); 169Please respect copyright.ＰＥＮＡＮＡgoKQa9RvC2
reader.onload = () => 169Please respect copyright.ＰＥＮＡＮＡemwXsV4eh1
{169Please respect copyright.ＰＥＮＡＮＡsXHnxF9lkb
let content_whole = new Uint8Array(reader.result);169Please respect copyright.ＰＥＮＡＮＡK6u5EWIJFe
}169Please respect copyright.ＰＥＮＡＮＡmhI8NzYElh
reader.readAsArrayBuffer(file);169Please respect copyright.ＰＥＮＡＮＡyxQgOsYFmW
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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:169Please respect copyright.ＰＥＮＡＮＡXR8ZqiC7mC
---read part of file content into array buffer---169Please respect copyright.ＰＥＮＡＮＡMdY4wyQmTP
let file=input.files[0], block_size=1000000, start=0, end=block_size; const reader = new FileReader(); 169Please respect copyright.ＰＥＮＡＮＡP2PMV4TXsa
reader.onload = () => 169Please respect copyright.ＰＥＮＡＮＡL8PKmgKcTO
{169Please respect copyright.ＰＥＮＡＮＡJqK8JAgPXd
let content_part = new Uint8Array(reader.result);169Please respect copyright.ＰＥＮＡＮＡ1ay4SkZhBN
}169Please respect copyright.ＰＥＮＡＮＡYocmgIoQSQ
reader.readAsArrayBuffer(file.slice(start,end));169Please respect copyright.ＰＥＮＡＮＡBUYZfCTHwW
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169Please respect copyright.ＰＥＮＡＮＡ0ePlawCmBK
Section X. Thanks169Please respect copyright.ＰＥＮＡＮＡT3YSFAznuo
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]169Please respect copyright.ＰＥＮＡＮＡplw2DCUunX
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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