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:18Please respect copyright.ＰＥＮＡＮＡ9dGyIayh8h
---read whole file content into array buffer---18Please respect copyright.ＰＥＮＡＮＡyB0HpJLOZB
let file=input.files[0]; const reader = new FileReader(); 18Please respect copyright.ＰＥＮＡＮＡS5co7Opk1p
reader.onload = () => 18Please respect copyright.ＰＥＮＡＮＡXt37KLmGpX
{18Please respect copyright.ＰＥＮＡＮＡNps6Ac65u6
let content_whole = new Uint8Array(reader.result);18Please respect copyright.ＰＥＮＡＮＡeXkbHHf1B5
}18Please respect copyright.ＰＥＮＡＮＡHtwyEG90Gg
reader.readAsArrayBuffer(file);18Please respect copyright.ＰＥＮＡＮＡyUs6zqj0Oz
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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:18Please respect copyright.ＰＥＮＡＮＡ8sZWjFDy7N
---read part of file content into array buffer---18Please respect copyright.ＰＥＮＡＮＡCQODMpspmK
let file=input.files[0], block_size=1000000, start=0, end=block_size; const reader = new FileReader(); 18Please respect copyright.ＰＥＮＡＮＡeK20pmOa1C
reader.onload = () => 18Please respect copyright.ＰＥＮＡＮＡKqcAwtKBPy
{18Please respect copyright.ＰＥＮＡＮＡOoblyP8shy
let content_part = new Uint8Array(reader.result);18Please respect copyright.ＰＥＮＡＮＡJ1x9cz3WCC
}18Please respect copyright.ＰＥＮＡＮＡyKE40aPzdY
reader.readAsArrayBuffer(file.slice(start,end));18Please respect copyright.ＰＥＮＡＮＡm9x5aJlpZk
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18Please respect copyright.ＰＥＮＡＮＡB29p6N0L5N
Section X. Thanks18Please respect copyright.ＰＥＮＡＮＡ284ek2KUC4
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.com18Please respect copyright.ＰＥＮＡＮＡP4xhBmgROx
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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