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:49Please respect copyright.ＰＥＮＡＮＡhziKBcJDxS
---read whole file content into array buffer---49Please respect copyright.ＰＥＮＡＮＡx5M5GUVqZ4
let file=input.files[0]; const reader = new FileReader(); 49Please respect copyright.ＰＥＮＡＮＡz0Dsr74IUb
reader.onload = () => 49Please respect copyright.ＰＥＮＡＮＡ9X2tH50gMl
{49Please respect copyright.ＰＥＮＡＮＡkIGqb33ha2
let content_whole = new Uint8Array(reader.result);49Please respect copyright.ＰＥＮＡＮＡstD8Q0j6Nu
}49Please respect copyright.ＰＥＮＡＮＡD17f9n7ssk
reader.readAsArrayBuffer(file);49Please respect copyright.ＰＥＮＡＮＡs5rFBUXsH8
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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:49Please respect copyright.ＰＥＮＡＮＡwyduGTkrGX
---read part of file content into array buffer---49Please respect copyright.ＰＥＮＡＮＡc2OII1nlh9
let file=input.files[0], block_size=1000000, start=0, end=block_size; const reader = new FileReader(); 49Please respect copyright.ＰＥＮＡＮＡp2fyNsv43y
reader.onload = () => 49Please respect copyright.ＰＥＮＡＮＡmQNpqMvIdp
{49Please respect copyright.ＰＥＮＡＮＡ5Nkj90jDk8
let content_part = new Uint8Array(reader.result);49Please respect copyright.ＰＥＮＡＮＡuu5rL94KbX
}49Please respect copyright.ＰＥＮＡＮＡ7uggMRfu6f
reader.readAsArrayBuffer(file.slice(start,end));49Please respect copyright.ＰＥＮＡＮＡv8a0giDCuv
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49Please respect copyright.ＰＥＮＡＮＡ1STgVlwB6m
Section X. Thanks49Please respect copyright.ＰＥＮＡＮＡHePnS7BVkO
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.com49Please respect copyright.ＰＥＮＡＮＡ3cHaszonkj
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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