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:55Please respect copyright.ＰＥＮＡＮＡakz06q9Cm6
---read whole file content into array buffer---55Please respect copyright.ＰＥＮＡＮＡxFoIltOzZ1
let file=input.files[0]; const reader = new FileReader(); 55Please respect copyright.ＰＥＮＡＮＡ9OYpneMvPs
reader.onload = () => 55Please respect copyright.ＰＥＮＡＮＡ9qjUbOMWFU
{55Please respect copyright.ＰＥＮＡＮＡ8eHvkf6OfA
let content_whole = new Uint8Array(reader.result);55Please respect copyright.ＰＥＮＡＮＡK5xvGscNVS
}55Please respect copyright.ＰＥＮＡＮＡyjWxSfGmtx
reader.readAsArrayBuffer(file);55Please respect copyright.ＰＥＮＡＮＡFfPevJJBMC
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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:55Please respect copyright.ＰＥＮＡＮＡW2BvnV60BV
---read part of file content into array buffer---55Please respect copyright.ＰＥＮＡＮＡp7VbzNcgfd
let file=input.files[0], block_size=1000000, start=0, end=block_size; const reader = new FileReader(); 55Please respect copyright.ＰＥＮＡＮＡpDXNRYGH2X
reader.onload = () => 55Please respect copyright.ＰＥＮＡＮＡpZD0r2R1R6
{55Please respect copyright.ＰＥＮＡＮＡgKOAOhaj4L
let content_part = new Uint8Array(reader.result);55Please respect copyright.ＰＥＮＡＮＡTIRx8RAldz
}55Please respect copyright.ＰＥＮＡＮＡQe4wYEvtvH
reader.readAsArrayBuffer(file.slice(start,end));55Please respect copyright.ＰＥＮＡＮＡr1n04mM4RW
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55Please respect copyright.ＰＥＮＡＮＡaOKqXzX1av
Section X. Thanks55Please respect copyright.ＰＥＮＡＮＡIivZkRevmX
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]55Please respect copyright.ＰＥＮＡＮＡKAMxhQOvGL
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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