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:25Please respect copyright.ＰＥＮＡＮＡ4hD2vL77kd
---read whole file content into array buffer---25Please respect copyright.ＰＥＮＡＮＡsXG9fREZ9p
let file=input.files[0]; const reader = new FileReader(); 25Please respect copyright.ＰＥＮＡＮＡdTrydrYGbc
reader.onload = () => 25Please respect copyright.ＰＥＮＡＮＡQNWfK5LXBx
{25Please respect copyright.ＰＥＮＡＮＡCUayOuS1Un
let content_whole = new Uint8Array(reader.result);25Please respect copyright.ＰＥＮＡＮＡKxWHOi3l0Q
}25Please respect copyright.ＰＥＮＡＮＡOMI3UwgoNr
reader.readAsArrayBuffer(file);25Please respect copyright.ＰＥＮＡＮＡqUEz0mS5fo
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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:25Please respect copyright.ＰＥＮＡＮＡvDF8PLerND
---read part of file content into array buffer---25Please respect copyright.ＰＥＮＡＮＡjdIR7mGzZ7
let file=input.files[0], block_size=1000000, start=0, end=block_size; const reader = new FileReader(); 25Please respect copyright.ＰＥＮＡＮＡbvoZVQMrP1
reader.onload = () => 25Please respect copyright.ＰＥＮＡＮＡWSy06431sm
{25Please respect copyright.ＰＥＮＡＮＡ0d9LUUD7Pt
let content_part = new Uint8Array(reader.result);25Please respect copyright.ＰＥＮＡＮＡj928t9A5Zs
}25Please respect copyright.ＰＥＮＡＮＡTZLKjDhLcQ
reader.readAsArrayBuffer(file.slice(start,end));25Please respect copyright.ＰＥＮＡＮＡZp82ASxgCQ
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25Please respect copyright.ＰＥＮＡＮＡErMRIAhcGi
Section X. Thanks25Please respect copyright.ＰＥＮＡＮＡff0KqmU7Ob
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.com25Please respect copyright.ＰＥＮＡＮＡ4WcaXogeWt
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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