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:29Please respect copyright.ＰＥＮＡＮＡL22kdWZIvf
---read whole file content into array buffer---29Please respect copyright.ＰＥＮＡＮＡzKxCfmfz7B
let file=input.files[0]; const reader = new FileReader(); 29Please respect copyright.ＰＥＮＡＮＡsJSxrQKEBL
reader.onload = () => 29Please respect copyright.ＰＥＮＡＮＡ7qSVijc2Cp
{29Please respect copyright.ＰＥＮＡＮＡuCAiOKNCKk
let content_whole = new Uint8Array(reader.result);29Please respect copyright.ＰＥＮＡＮＡzwZsqmxns8
}29Please respect copyright.ＰＥＮＡＮＡws8mI9hIQl
reader.readAsArrayBuffer(file);29Please respect copyright.ＰＥＮＡＮＡ2XNeiDKVhD
-----------------------------------------------
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:29Please respect copyright.ＰＥＮＡＮＡGqZPZIaOQv
---read part of file content into array buffer---29Please respect copyright.ＰＥＮＡＮＡlVxQhUsNb4
let file=input.files[0], block_size=1000000, start=0, end=block_size; const reader = new FileReader(); 29Please respect copyright.ＰＥＮＡＮＡMjyANZwSWX
reader.onload = () => 29Please respect copyright.ＰＥＮＡＮＡhH0G1i0bKH
{29Please respect copyright.ＰＥＮＡＮＡ5hYD0wWVnD
let content_part = new Uint8Array(reader.result);29Please respect copyright.ＰＥＮＡＮＡ1e4FOZRE9W
}29Please respect copyright.ＰＥＮＡＮＡxIMUE67mq2
reader.readAsArrayBuffer(file.slice(start,end));29Please respect copyright.ＰＥＮＡＮＡwidIfc08lC
-----------------------------------------------
29Please respect copyright.ＰＥＮＡＮＡ3EOM3xdJM1
Section X. Thanks29Please respect copyright.ＰＥＮＡＮＡKrAqu4p0DT
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.com29Please respect copyright.ＰＥＮＡＮＡcsYySJtari
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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