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:72Please respect copyright.ＰＥＮＡＮＡSAYi9NpPI4
---read whole file content into array buffer---72Please respect copyright.ＰＥＮＡＮＡ0xiXHUqNAd
let file=input.files[0]; const reader = new FileReader(); 72Please respect copyright.ＰＥＮＡＮＡaiwzYgkTMs
reader.onload = () => 72Please respect copyright.ＰＥＮＡＮＡYN4gxAhyJN
{72Please respect copyright.ＰＥＮＡＮＡ26ch8Ls1S5
let content_whole = new Uint8Array(reader.result);72Please respect copyright.ＰＥＮＡＮＡCbZFnRwTyS
}72Please respect copyright.ＰＥＮＡＮＡSDH8SC9W3P
reader.readAsArrayBuffer(file);72Please respect copyright.ＰＥＮＡＮＡwWTnLLJKy4
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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:72Please respect copyright.ＰＥＮＡＮＡFMgxbUToUR
---read part of file content into array buffer---72Please respect copyright.ＰＥＮＡＮＡykyTbXKTDY
let file=input.files[0], block_size=1000000, start=0, end=block_size; const reader = new FileReader(); 72Please respect copyright.ＰＥＮＡＮＡGvfw8uCWhe
reader.onload = () => 72Please respect copyright.ＰＥＮＡＮＡteMyMZp9qJ
{72Please respect copyright.ＰＥＮＡＮＡJeOZrtQrZB
let content_part = new Uint8Array(reader.result);72Please respect copyright.ＰＥＮＡＮＡ5jQsr5odN3
}72Please respect copyright.ＰＥＮＡＮＡipjK2BzI61
reader.readAsArrayBuffer(file.slice(start,end));72Please respect copyright.ＰＥＮＡＮＡnRfrW2QXQJ
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72Please respect copyright.ＰＥＮＡＮＡ6nJkyVJjdo
Section X. Thanks72Please respect copyright.ＰＥＮＡＮＡHfpuZgVvTi
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]72Please respect copyright.ＰＥＮＡＮＡphSH8zzQDB
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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