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。1234 copyright protection292ＰＥＮＡＮＡdIWYRCQVy6 尼

When user select a file by <input type=file>, its content can be read by javascript like this:296Please respect copyright.ＰＥＮＡＮＡNQfGnqlJfZ
---read whole file content into array buffer---296Please respect copyright.ＰＥＮＡＮＡPKhl4PH73x
let file=input.files[0]; const reader = new FileReader(); 296Please respect copyright.ＰＥＮＡＮＡm5l6lKKH0c
reader.onload = () => 296Please respect copyright.ＰＥＮＡＮＡ5whqWS0kCb
{296Please respect copyright.ＰＥＮＡＮＡ1UD4MkgunH
  let content_whole = new Uint8Array(reader.result);296Please respect copyright.ＰＥＮＡＮＡx0KPl41J5C
}296Please respect copyright.ＰＥＮＡＮＡxAumtNTTZ4
reader.readAsArrayBuffer(file);296Please respect copyright.ＰＥＮＡＮＡeecBOwD22Q
-----------------------------------------------1234 copyright protection292ＰＥＮＡＮＡSyLmHgzzOi 尼

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:296Please respect copyright.ＰＥＮＡＮＡ82Q67tvskg
---read part of file content into array buffer---296Please respect copyright.ＰＥＮＡＮＡGf2XsI6p5G
let file=input.files[0], block_size=1000000, start=0, end=block_size; const reader = new FileReader(); 296Please respect copyright.ＰＥＮＡＮＡ2J0IWzGvaQ
reader.onload = () => 296Please respect copyright.ＰＥＮＡＮＡKQLqWJWFJa
{296Please respect copyright.ＰＥＮＡＮＡmUAdKLV43N
  let content_part = new Uint8Array(reader.result);296Please respect copyright.ＰＥＮＡＮＡhWKoxTNbJk
}296Please respect copyright.ＰＥＮＡＮＡApne2t5U7L
reader.readAsArrayBuffer(file.slice(start,end));296Please respect copyright.ＰＥＮＡＮＡpOGqBA0kP8
-----------------------------------------------1234 copyright protection292ＰＥＮＡＮＡ0zKSa1r5qm 尼

296Please respect copyright.ＰＥＮＡＮＡnULuY7ayG3
Section X. Thanks296Please respect copyright.ＰＥＮＡＮＡmx8smCn2e5
https://segmentfault.com/a/11900000221136051234 copyright protection292ＰＥＮＡＮＡ8Syj9zLjrn 尼

Section Y. Contacts Me1234 copyright protection292ＰＥＮＡＮＡlOZjYf4SAd 尼

If you found any errors or have any suggestions for this article, please let me know, my wechat: si_jinmin, my email: [email protected]296Please respect copyright.ＰＥＮＡＮＡQrT7yHfiCy
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]1234 copyright protection292ＰＥＮＡＮＡfatxylc7Hm 尼

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