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:159Please respect copyright.ＰＥＮＡＮＡZhKGQsYvfL
---read whole file content into array buffer---159Please respect copyright.ＰＥＮＡＮＡPmpevnr4DC
let file=input.files[0]; const reader = new FileReader(); 159Please respect copyright.ＰＥＮＡＮＡO5yaM77d5Q
reader.onload = () => 159Please respect copyright.ＰＥＮＡＮＡaeQbGvnwuV
{159Please respect copyright.ＰＥＮＡＮＡmiJD4ZAxax
let content_whole = new Uint8Array(reader.result);159Please respect copyright.ＰＥＮＡＮＡ6veXqC7mj2
}159Please respect copyright.ＰＥＮＡＮＡsFaM6t7Zet
reader.readAsArrayBuffer(file);159Please respect copyright.ＰＥＮＡＮＡw36T4SJni3
-----------------------------------------------
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:159Please respect copyright.ＰＥＮＡＮＡf7hnWnN4D9
---read part of file content into array buffer---159Please respect copyright.ＰＥＮＡＮＡXeRP6Lt0bA
let file=input.files[0], block_size=1000000, start=0, end=block_size; const reader = new FileReader(); 159Please respect copyright.ＰＥＮＡＮＡYKEGlz68tO
reader.onload = () => 159Please respect copyright.ＰＥＮＡＮＡp6im8l0B6q
{159Please respect copyright.ＰＥＮＡＮＡtnAa5cxsPu
let content_part = new Uint8Array(reader.result);159Please respect copyright.ＰＥＮＡＮＡVRsqJ06y3Q
}159Please respect copyright.ＰＥＮＡＮＡqzCN0flpzQ
reader.readAsArrayBuffer(file.slice(start,end));159Please respect copyright.ＰＥＮＡＮＡCJ7yaMd8qt
-----------------------------------------------
159Please respect copyright.ＰＥＮＡＮＡBUQjrqezh4
Section X. Thanks159Please respect copyright.ＰＥＮＡＮＡdF2p6JgB5C
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]159Please respect copyright.ＰＥＮＡＮＡqGoBcuI9tS
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]
如果您對C/C++ Programming, Linux, HTTP Protocol, Website Development, Vue, Git, VsCode感興趣，邀請您加入「Linux/C/C++ Website Development」微信群，請加我的微信（si_jinmin）以便拉您进群。
ns216.73.216.160da2
