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:156Please respect copyright.ＰＥＮＡＮＡ9OGmFDoxsj
---read whole file content into array buffer---156Please respect copyright.ＰＥＮＡＮＡrnCGXRDjIq
let file=input.files[0]; const reader = new FileReader(); 156Please respect copyright.ＰＥＮＡＮＡvBJZIjcEpi
reader.onload = () => 156Please respect copyright.ＰＥＮＡＮＡPdSKqDENZi
{156Please respect copyright.ＰＥＮＡＮＡZP8wGZtyAi
let content_whole = new Uint8Array(reader.result);156Please respect copyright.ＰＥＮＡＮＡ5alkm7FsTV
}156Please respect copyright.ＰＥＮＡＮＡp7oSOrydZV
reader.readAsArrayBuffer(file);156Please respect copyright.ＰＥＮＡＮＡ7PYW9ssfKz
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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:156Please respect copyright.ＰＥＮＡＮＡQuqBoac4fd
---read part of file content into array buffer---156Please respect copyright.ＰＥＮＡＮＡuXl3KpwDUv
let file=input.files[0], block_size=1000000, start=0, end=block_size; const reader = new FileReader(); 156Please respect copyright.ＰＥＮＡＮＡZ2bc68CcPC
reader.onload = () => 156Please respect copyright.ＰＥＮＡＮＡDngsjBwNRx
{156Please respect copyright.ＰＥＮＡＮＡ6jclbxATJ6
let content_part = new Uint8Array(reader.result);156Please respect copyright.ＰＥＮＡＮＡljuzZ9BdLs
}156Please respect copyright.ＰＥＮＡＮＡEjQfk5hlvL
reader.readAsArrayBuffer(file.slice(start,end));156Please respect copyright.ＰＥＮＡＮＡWVfEMcnTka
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156Please respect copyright.ＰＥＮＡＮＡ41z0cHd9Ch
Section X. Thanks156Please respect copyright.ＰＥＮＡＮＡBOy4KYwuD1
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]156Please respect copyright.ＰＥＮＡＮＡcqYz9ZGrLD
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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