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:58Please respect copyright.ＰＥＮＡＮＡ01eLfBb4rN
---read whole file content into array buffer---58Please respect copyright.ＰＥＮＡＮＡSvg4PEn69U
let file=input.files[0]; const reader = new FileReader(); 58Please respect copyright.ＰＥＮＡＮＡTbSGUBFxaw
reader.onload = () => 58Please respect copyright.ＰＥＮＡＮＡLrQPtiHbBw
{58Please respect copyright.ＰＥＮＡＮＡphqGGuHcQI
let content_whole = new Uint8Array(reader.result);58Please respect copyright.ＰＥＮＡＮＡ6Sjx0y6jLc
}58Please respect copyright.ＰＥＮＡＮＡPFiD1DoL0s
reader.readAsArrayBuffer(file);58Please respect copyright.ＰＥＮＡＮＡQWXBUKpOUc
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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:58Please respect copyright.ＰＥＮＡＮＡSeL7cvX8gu
---read part of file content into array buffer---58Please respect copyright.ＰＥＮＡＮＡwYxylerrcy
let file=input.files[0], block_size=1000000, start=0, end=block_size; const reader = new FileReader(); 58Please respect copyright.ＰＥＮＡＮＡIii25vkkLG
reader.onload = () => 58Please respect copyright.ＰＥＮＡＮＡV8qbTsbq4V
{58Please respect copyright.ＰＥＮＡＮＡKd7WIxAQoJ
let content_part = new Uint8Array(reader.result);58Please respect copyright.ＰＥＮＡＮＡbHAgdIcyLG
}58Please respect copyright.ＰＥＮＡＮＡIPviHdHaQv
reader.readAsArrayBuffer(file.slice(start,end));58Please respect copyright.ＰＥＮＡＮＡtgeSxcAFZv
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58Please respect copyright.ＰＥＮＡＮＡYgJ2IYIGln
Section X. Thanks58Please respect copyright.ＰＥＮＡＮＡTbhc6BATpa
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]58Please respect copyright.ＰＥＮＡＮＡGI7j21ax6S
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