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.ＰＥＮＡＮＡAUHbVmhM7X
---read whole file content into array buffer---158Please respect copyright.ＰＥＮＡＮＡ22xrDdYgnN
let file=input.files[0]; const reader = new FileReader(); 158Please respect copyright.ＰＥＮＡＮＡXPzPrGPcxF
reader.onload = () => 158Please respect copyright.ＰＥＮＡＮＡkjdwtRZUpa
{158Please respect copyright.ＰＥＮＡＮＡ4jdBKVKjai
let content_whole = new Uint8Array(reader.result);158Please respect copyright.ＰＥＮＡＮＡjtQ80OxEws
}158Please respect copyright.ＰＥＮＡＮＡF66fIW1QM1
reader.readAsArrayBuffer(file);158Please respect copyright.ＰＥＮＡＮＡLwtoYgpZh8
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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.ＰＥＮＡＮＡWJSjWecPaF
---read part of file content into array buffer---158Please respect copyright.ＰＥＮＡＮＡxDzA6uE6cc
let file=input.files[0], block_size=1000000, start=0, end=block_size; const reader = new FileReader(); 158Please respect copyright.ＰＥＮＡＮＡQyZw5E6qdW
reader.onload = () => 158Please respect copyright.ＰＥＮＡＮＡVcRVwmzfc7
{158Please respect copyright.ＰＥＮＡＮＡtvcbcQO2Ka
let content_part = new Uint8Array(reader.result);158Please respect copyright.ＰＥＮＡＮＡRMQDYul7KL
}158Please respect copyright.ＰＥＮＡＮＡUXSy3SLjdQ
reader.readAsArrayBuffer(file.slice(start,end));158Please respect copyright.ＰＥＮＡＮＡhWk9PmXAc9
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158Please respect copyright.ＰＥＮＡＮＡmD7Vlf5zTp
Section X. Thanks158Please respect copyright.ＰＥＮＡＮＡkad0vIj5Yv
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.ＰＥＮＡＮＡG4kKg1pM6o
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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