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:158Please respect copyright.ＰＥＮＡＮＡFPasnizCpe
---read whole file content into array buffer---158Please respect copyright.ＰＥＮＡＮＡYj66Bh2qnX
let file=input.files[0]; const reader = new FileReader(); 158Please respect copyright.ＰＥＮＡＮＡoBBpNPgNgt
reader.onload = () => 158Please respect copyright.ＰＥＮＡＮＡktQQjtqnro
{158Please respect copyright.ＰＥＮＡＮＡAg5AihF32t
let content_whole = new Uint8Array(reader.result);158Please respect copyright.ＰＥＮＡＮＡEts722ATEK
}158Please respect copyright.ＰＥＮＡＮＡJASWS5plUs
reader.readAsArrayBuffer(file);158Please respect copyright.ＰＥＮＡＮＡBGVuA7zLVi
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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:158Please respect copyright.ＰＥＮＡＮＡSxLSBVbyYj
---read part of file content into array buffer---158Please respect copyright.ＰＥＮＡＮＡ1JCxGt1m9D
let file=input.files[0], block_size=1000000, start=0, end=block_size; const reader = new FileReader(); 158Please respect copyright.ＰＥＮＡＮＡgA9Vm4T8cJ
reader.onload = () => 158Please respect copyright.ＰＥＮＡＮＡWFEUVN58BY
{158Please respect copyright.ＰＥＮＡＮＡOnBLCQgCza
let content_part = new Uint8Array(reader.result);158Please respect copyright.ＰＥＮＡＮＡompw8vQYXP
}158Please respect copyright.ＰＥＮＡＮＡHQ2EEElhUN
reader.readAsArrayBuffer(file.slice(start,end));158Please respect copyright.ＰＥＮＡＮＡs5w72aZt5l
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158Please respect copyright.ＰＥＮＡＮＡFWU0YLPRmE
Section X. Thanks158Please respect copyright.ＰＥＮＡＮＡ4bgTyOqbew
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]158Please respect copyright.ＰＥＮＡＮＡA8bhjW40H3
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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