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:31Please respect copyright.ＰＥＮＡＮＡagEsqel2xi
---read whole file content into array buffer---31Please respect copyright.ＰＥＮＡＮＡ5GUbOPn9zp
let file=input.files[0]; const reader = new FileReader(); 31Please respect copyright.ＰＥＮＡＮＡHL0jrQcYka
reader.onload = () => 31Please respect copyright.ＰＥＮＡＮＡBOP0ZLt2iJ
{31Please respect copyright.ＰＥＮＡＮＡAGMxVzohRn
let content_whole = new Uint8Array(reader.result);31Please respect copyright.ＰＥＮＡＮＡVG5ec64uJ0
}31Please respect copyright.ＰＥＮＡＮＡtOVAeOOQju
reader.readAsArrayBuffer(file);31Please respect copyright.ＰＥＮＡＮＡgvB7d4S0t6
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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:31Please respect copyright.ＰＥＮＡＮＡOdHxASX1MT
---read part of file content into array buffer---31Please respect copyright.ＰＥＮＡＮＡac0jwx4DLF
let file=input.files[0], block_size=1000000, start=0, end=block_size; const reader = new FileReader(); 31Please respect copyright.ＰＥＮＡＮＡlZM8ouQR2D
reader.onload = () => 31Please respect copyright.ＰＥＮＡＮＡQkmGdBcQGj
{31Please respect copyright.ＰＥＮＡＮＡuofMSjvugS
let content_part = new Uint8Array(reader.result);31Please respect copyright.ＰＥＮＡＮＡbF3qjud7gY
}31Please respect copyright.ＰＥＮＡＮＡ6S2jg2SCOF
reader.readAsArrayBuffer(file.slice(start,end));31Please respect copyright.ＰＥＮＡＮＡltiaI6f4id
-----------------------------------------------
31Please respect copyright.ＰＥＮＡＮＡp5AwKkG6gy
Section X. Thanks31Please respect copyright.ＰＥＮＡＮＡMZtfLNRpGQ
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.com31Please respect copyright.ＰＥＮＡＮＡ6cdck84sco
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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