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:158Please respect copyright.ＰＥＮＡＮＡUle2Bynf2P
---read whole file content into array buffer---158Please respect copyright.ＰＥＮＡＮＡw2hk01mh87
let file=input.files[0]; const reader = new FileReader(); 158Please respect copyright.ＰＥＮＡＮＡ1kKv20anh4
reader.onload = () => 158Please respect copyright.ＰＥＮＡＮＡKfVR4acWrC
{158Please respect copyright.ＰＥＮＡＮＡWB0F1lLm6A
let content_whole = new Uint8Array(reader.result);158Please respect copyright.ＰＥＮＡＮＡpg4u5vK06L
}158Please respect copyright.ＰＥＮＡＮＡ7Mz8t5JaY5
reader.readAsArrayBuffer(file);158Please respect copyright.ＰＥＮＡＮＡUXb5Dzh5iC
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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:158Please respect copyright.ＰＥＮＡＮＡ1kQ622tC7V
---read part of file content into array buffer---158Please respect copyright.ＰＥＮＡＮＡrbXD61IRo4
let file=input.files[0], block_size=1000000, start=0, end=block_size; const reader = new FileReader(); 158Please respect copyright.ＰＥＮＡＮＡbbE44RItfY
reader.onload = () => 158Please respect copyright.ＰＥＮＡＮＡvTrbdqBMbu
{158Please respect copyright.ＰＥＮＡＮＡPeT6jftYgY
let content_part = new Uint8Array(reader.result);158Please respect copyright.ＰＥＮＡＮＡtzgKdSyLsi
}158Please respect copyright.ＰＥＮＡＮＡrsaFTJ5pua
reader.readAsArrayBuffer(file.slice(start,end));158Please respect copyright.ＰＥＮＡＮＡXI21myPxiZ
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158Please respect copyright.ＰＥＮＡＮＡXZy2TYqPUp
Section X. Thanks158Please respect copyright.ＰＥＮＡＮＡWQBgTVD4Ri
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]158Please respect copyright.ＰＥＮＡＮＡUNvjcfiznO
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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