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:174Please respect copyright.ＰＥＮＡＮＡ8MYrCwXLMJ
---read whole file content into array buffer---174Please respect copyright.ＰＥＮＡＮＡXKKkFJQQV9
let file=input.files[0]; const reader = new FileReader(); 174Please respect copyright.ＰＥＮＡＮＡ8AES08gh4I
reader.onload = () => 174Please respect copyright.ＰＥＮＡＮＡg74WyBA4Qh
{174Please respect copyright.ＰＥＮＡＮＡALcqRFzvGu
let content_whole = new Uint8Array(reader.result);174Please respect copyright.ＰＥＮＡＮＡ7Px1thVzmR
}174Please respect copyright.ＰＥＮＡＮＡW23V7zRLO1
reader.readAsArrayBuffer(file);174Please respect copyright.ＰＥＮＡＮＡBti3JPUs6d
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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:174Please respect copyright.ＰＥＮＡＮＡmdu6l8azN3
---read part of file content into array buffer---174Please respect copyright.ＰＥＮＡＮＡr30rjDfYSc
let file=input.files[0], block_size=1000000, start=0, end=block_size; const reader = new FileReader(); 174Please respect copyright.ＰＥＮＡＮＡaGwxw6gvEr
reader.onload = () => 174Please respect copyright.ＰＥＮＡＮＡwBiYh8b6xA
{174Please respect copyright.ＰＥＮＡＮＡo2VQtcOQ9V
let content_part = new Uint8Array(reader.result);174Please respect copyright.ＰＥＮＡＮＡRS2SK29Ryk
}174Please respect copyright.ＰＥＮＡＮＡcnABFsTjHf
reader.readAsArrayBuffer(file.slice(start,end));174Please respect copyright.ＰＥＮＡＮＡI0ZhpsGeio
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174Please respect copyright.ＰＥＮＡＮＡYRD3eeL2x3
Section X. Thanks174Please respect copyright.ＰＥＮＡＮＡbtpsstz9XQ
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]174Please respect copyright.ＰＥＮＡＮＡnOhSBcNzVC
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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