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:171Please respect copyright.ＰＥＮＡＮＡn8POFPonjH
---read whole file content into array buffer---171Please respect copyright.ＰＥＮＡＮＡHTpMXBWJ7B
let file=input.files[0]; const reader = new FileReader(); 171Please respect copyright.ＰＥＮＡＮＡnNzlrEAgqK
reader.onload = () => 171Please respect copyright.ＰＥＮＡＮＡDO3NZy6gOw
{171Please respect copyright.ＰＥＮＡＮＡyXIzIGoRi0
let content_whole = new Uint8Array(reader.result);171Please respect copyright.ＰＥＮＡＮＡPjpNjPbDuY
}171Please respect copyright.ＰＥＮＡＮＡYKZUCJOCt6
reader.readAsArrayBuffer(file);171Please respect copyright.ＰＥＮＡＮＡRcNvsxA1Fm
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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:171Please respect copyright.ＰＥＮＡＮＡTHmISaTltj
---read part of file content into array buffer---171Please respect copyright.ＰＥＮＡＮＡXrN7gL3XDo
let file=input.files[0], block_size=1000000, start=0, end=block_size; const reader = new FileReader(); 171Please respect copyright.ＰＥＮＡＮＡ1MZldQXH4O
reader.onload = () => 171Please respect copyright.ＰＥＮＡＮＡ1X2DOFuV12
{171Please respect copyright.ＰＥＮＡＮＡTiGtvAOhup
let content_part = new Uint8Array(reader.result);171Please respect copyright.ＰＥＮＡＮＡijxafm4q6Q
}171Please respect copyright.ＰＥＮＡＮＡm3EKuUtrDz
reader.readAsArrayBuffer(file.slice(start,end));171Please respect copyright.ＰＥＮＡＮＡCJpk73CoBL
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171Please respect copyright.ＰＥＮＡＮＡVvP8sp5Y9f
Section X. Thanks171Please respect copyright.ＰＥＮＡＮＡUnD6l4pwOz
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]171Please respect copyright.ＰＥＮＡＮＡ3toAsfHpb0
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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