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:178Please respect copyright.ＰＥＮＡＮＡpFa0xQZDx0
---read whole file content into array buffer---178Please respect copyright.ＰＥＮＡＮＡGoekjPnEBj
let file=input.files[0]; const reader = new FileReader(); 178Please respect copyright.ＰＥＮＡＮＡytFOUQOEDB
reader.onload = () => 178Please respect copyright.ＰＥＮＡＮＡNdHP0Lht7R
{178Please respect copyright.ＰＥＮＡＮＡ2wFwxSyX2n
let content_whole = new Uint8Array(reader.result);178Please respect copyright.ＰＥＮＡＮＡ9Jv8u8LTMD
}178Please respect copyright.ＰＥＮＡＮＡYKA6Mjsmtt
reader.readAsArrayBuffer(file);178Please respect copyright.ＰＥＮＡＮＡY3GOhQL1VA
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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:178Please respect copyright.ＰＥＮＡＮＡ3Tmh2DhcNn
---read part of file content into array buffer---178Please respect copyright.ＰＥＮＡＮＡhQKKDxXTPH
let file=input.files[0], block_size=1000000, start=0, end=block_size; const reader = new FileReader(); 178Please respect copyright.ＰＥＮＡＮＡAvFBtBcKP9
reader.onload = () => 178Please respect copyright.ＰＥＮＡＮＡnLRIF1qUhO
{178Please respect copyright.ＰＥＮＡＮＡYbKaVJQ39l
let content_part = new Uint8Array(reader.result);178Please respect copyright.ＰＥＮＡＮＡjwONVuisNw
}178Please respect copyright.ＰＥＮＡＮＡmDJxqQWc4D
reader.readAsArrayBuffer(file.slice(start,end));178Please respect copyright.ＰＥＮＡＮＡn8xlAWN7VC
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178Please respect copyright.ＰＥＮＡＮＡlj7muZ08Pq
Section X. Thanks178Please respect copyright.ＰＥＮＡＮＡGg0Pmg8rj5
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]178Please respect copyright.ＰＥＮＡＮＡ5AHJEBqqZN
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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