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:38Please respect copyright.ＰＥＮＡＮＡjhVthyVywF
---read whole file content into array buffer---38Please respect copyright.ＰＥＮＡＮＡvFmPH63PUv
let file=input.files[0]; const reader = new FileReader(); 38Please respect copyright.ＰＥＮＡＮＡsuEnoz2TYr
reader.onload = () => 38Please respect copyright.ＰＥＮＡＮＡaJXSqx5Jj1
{38Please respect copyright.ＰＥＮＡＮＡIUtBpomHGq
let content_whole = new Uint8Array(reader.result);38Please respect copyright.ＰＥＮＡＮＡUKc4O4G5dh
}38Please respect copyright.ＰＥＮＡＮＡ257nVgwaJS
reader.readAsArrayBuffer(file);38Please respect copyright.ＰＥＮＡＮＡE08xMJez6w
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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:38Please respect copyright.ＰＥＮＡＮＡYpaIPTU1mD
---read part of file content into array buffer---38Please respect copyright.ＰＥＮＡＮＡgItfBiXCKO
let file=input.files[0], block_size=1000000, start=0, end=block_size; const reader = new FileReader(); 38Please respect copyright.ＰＥＮＡＮＡ9dhRx1jVrK
reader.onload = () => 38Please respect copyright.ＰＥＮＡＮＡr4UPTjeOl5
{38Please respect copyright.ＰＥＮＡＮＡSuy8FuIDrO
let content_part = new Uint8Array(reader.result);38Please respect copyright.ＰＥＮＡＮＡrgJ4ayakAX
}38Please respect copyright.ＰＥＮＡＮＡabhxLhKMhN
reader.readAsArrayBuffer(file.slice(start,end));38Please respect copyright.ＰＥＮＡＮＡCKdc0ynGJt
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38Please respect copyright.ＰＥＮＡＮＡE1EQImSS2V
Section X. Thanks38Please respect copyright.ＰＥＮＡＮＡlWHHLxwDlU
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.com38Please respect copyright.ＰＥＮＡＮＡZnSLqdKMg9
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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