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:137Please respect copyright.ＰＥＮＡＮＡA86AnDsREy
---read whole file content into array buffer---137Please respect copyright.ＰＥＮＡＮＡzQE5EgFLcy
let file=input.files[0]; const reader = new FileReader(); 137Please respect copyright.ＰＥＮＡＮＡpivvFnQbS3
reader.onload = () => 137Please respect copyright.ＰＥＮＡＮＡfmKVOsAeZl
{137Please respect copyright.ＰＥＮＡＮＡtcdpHHAa85
let content_whole = new Uint8Array(reader.result);137Please respect copyright.ＰＥＮＡＮＡz63V0Er1WA
}137Please respect copyright.ＰＥＮＡＮＡikpy2EeuDC
reader.readAsArrayBuffer(file);137Please respect copyright.ＰＥＮＡＮＡbPC5SDAnPY
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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:137Please respect copyright.ＰＥＮＡＮＡ5GAq8SOoJD
---read part of file content into array buffer---137Please respect copyright.ＰＥＮＡＮＡJefrpXhxWi
let file=input.files[0], block_size=1000000, start=0, end=block_size; const reader = new FileReader(); 137Please respect copyright.ＰＥＮＡＮＡucZCywHhAA
reader.onload = () => 137Please respect copyright.ＰＥＮＡＮＡDoL9IxEn82
{137Please respect copyright.ＰＥＮＡＮＡRl0Qnsiuy9
let content_part = new Uint8Array(reader.result);137Please respect copyright.ＰＥＮＡＮＡi47H5fcd05
}137Please respect copyright.ＰＥＮＡＮＡTlJN0icrHT
reader.readAsArrayBuffer(file.slice(start,end));137Please respect copyright.ＰＥＮＡＮＡ4ygbjBSYba
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137Please respect copyright.ＰＥＮＡＮＡdWxA5BfEc1
Section X. Thanks137Please respect copyright.ＰＥＮＡＮＡPKyncjbaMw
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]137Please respect copyright.ＰＥＮＡＮＡrDayNT6K2v
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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