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:123Please respect copyright.ＰＥＮＡＮＡ2esZ88Ysl8
---read whole file content into array buffer---123Please respect copyright.ＰＥＮＡＮＡM1K3F10f8M
let file=input.files[0]; const reader = new FileReader(); 123Please respect copyright.ＰＥＮＡＮＡiHSETNefgu
reader.onload = () => 123Please respect copyright.ＰＥＮＡＮＡ2XUaObq1Pe
{123Please respect copyright.ＰＥＮＡＮＡpKOuae9tFh
let content_whole = new Uint8Array(reader.result);123Please respect copyright.ＰＥＮＡＮＡNasyNEzLYe
}123Please respect copyright.ＰＥＮＡＮＡg6kokkAnxj
reader.readAsArrayBuffer(file);123Please respect copyright.ＰＥＮＡＮＡgoJkrw6eh5
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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:123Please respect copyright.ＰＥＮＡＮＡ8W4uXG8VfC
---read part of file content into array buffer---123Please respect copyright.ＰＥＮＡＮＡDSEJFeBGs0
let file=input.files[0], block_size=1000000, start=0, end=block_size; const reader = new FileReader(); 123Please respect copyright.ＰＥＮＡＮＡ23sueeYyHX
reader.onload = () => 123Please respect copyright.ＰＥＮＡＮＡ8OyeS305wy
{123Please respect copyright.ＰＥＮＡＮＡynox6r4vwj
let content_part = new Uint8Array(reader.result);123Please respect copyright.ＰＥＮＡＮＡ96fVRgmgN8
}123Please respect copyright.ＰＥＮＡＮＡBGUyre05y0
reader.readAsArrayBuffer(file.slice(start,end));123Please respect copyright.ＰＥＮＡＮＡ9TKxmnP4ZS
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123Please respect copyright.ＰＥＮＡＮＡmBeStsichb
Section X. Thanks123Please respect copyright.ＰＥＮＡＮＡZokDzBmq0x
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.com123Please respect copyright.ＰＥＮＡＮＡfQgRi8Cyfd
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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