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:17Please respect copyright.ＰＥＮＡＮＡ5FGryRKtiR
---read whole file content into array buffer---17Please respect copyright.ＰＥＮＡＮＡcjaSY7LYg8
let file=input.files[0]; const reader = new FileReader(); 17Please respect copyright.ＰＥＮＡＮＡepGC5gkO0K
reader.onload = () => 17Please respect copyright.ＰＥＮＡＮＡ3FJb8e2XQY
{17Please respect copyright.ＰＥＮＡＮＡ6veoZKDdZY
let content_whole = new Uint8Array(reader.result);17Please respect copyright.ＰＥＮＡＮＡDoIn0Irejq
}17Please respect copyright.ＰＥＮＡＮＡGILgECjuU8
reader.readAsArrayBuffer(file);17Please respect copyright.ＰＥＮＡＮＡakFxl0Phq2
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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:17Please respect copyright.ＰＥＮＡＮＡW7aIkEV4fS
---read part of file content into array buffer---17Please respect copyright.ＰＥＮＡＮＡXvoizbY96S
let file=input.files[0], block_size=1000000, start=0, end=block_size; const reader = new FileReader(); 17Please respect copyright.ＰＥＮＡＮＡhCkXEVGUOT
reader.onload = () => 17Please respect copyright.ＰＥＮＡＮＡslE6pbvRfv
{17Please respect copyright.ＰＥＮＡＮＡCI3vF6WvyW
let content_part = new Uint8Array(reader.result);17Please respect copyright.ＰＥＮＡＮＡPIzs5uuMIj
}17Please respect copyright.ＰＥＮＡＮＡCuqYyNSLgb
reader.readAsArrayBuffer(file.slice(start,end));17Please respect copyright.ＰＥＮＡＮＡwyhWdyMVSO
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17Please respect copyright.ＰＥＮＡＮＡdKTj0PfrRX
Section X. Thanks17Please respect copyright.ＰＥＮＡＮＡvbvc8sjwvh
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: si.jinmin@gmail.com17Please respect copyright.ＰＥＮＡＮＡTUhZajvsIC
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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