我用express 3在node.js中创建了一个文件上传函数。
我想抓取图像的文件扩展名。所以我可以重命名文件，然后附加文件扩展名。
app.post('/upload', function(req, res, next) {
var is = fs.createReadStream(req.files.upload.path),
fileExt = '', // I want to get the extension of the image here
os = fs.createWriteStream('public/images/users/' + req.session.adress + '.' + fileExt);
});
如何在node.js中获得图像的扩展名?
当前回答
下面的函数分割字符串并返回名称和扩展名，无论扩展名中有多少个点。如果没有扩展名，则返回空字符串。以点和/或空格开头的名字也可以。
function basext(name) {
name = name.trim()
const match = name.match(/^(\.+)/)
let prefix = ''
if (match) {
prefix = match[0]
name = name.replace(prefix, '')
}
const index = name.indexOf('.')
const ext = name.substring(index + 1)
const base = name.substring(0, index) || ext
return [prefix + base, base === ext ? '' : ext]
}
const [base, ext] = basext('hello.txt')
其他回答
// you can send full url here
function getExtension(filename) {
return filename.split('.').pop();
}
如果您正在使用express，请在配置中间件时添加以下行(bodyParser)
app.use(express.bodyParser({ keepExtensions: true}));
我认为在请求中映射Content-Type头也可以。这将工作的情况下，即使你上传的文件没有扩展名。 (当文件名在请求中没有扩展名)
假设您正在使用HTTP POST发送数据:
POST /upload2 HTTP/1.1
Host: localhost:7098
Connection: keep-alive
Content-Length: 1047799
Accept: */*
Origin: http://localhost:63342
User-Agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/51.0.2704.106 Safari/537.36
Content-Type: multipart/form-data; boundary=---- WebKitFormBoundaryPDULZN8DYK3VppPp
Referer: http://localhost:63342/Admin/index.html? _ijt=3a6a054pasorvrljf8t8ea0j4h
Accept-Encoding: gzip, deflate
Accept-Language: en-US,en;q=0.8,az;q=0.6,tr;q=0.4
Request Payload
------WebKitFormBoundaryPDULZN8DYK3VppPp
Content-Disposition: form-data; name="image"; filename="blob"
Content-Type: image/png
------WebKitFormBoundaryPDULZN8DYK3VppPp--
这里name Content-Type头包含数据的mime类型。 将此mime类型映射到扩展名将得到文件扩展名:)。
Restify BodyParser将此头文件转换为名称类型的属性
File {
domain:
Domain {
domain: null,
_events: { .... },
_eventsCount: 1,
_maxListeners: undefined,
members: [ ... ] },
_events: {},
_eventsCount: 0,
_maxListeners: undefined,
size: 1047621,
path: '/tmp/upload_2a4ac9ef22f7156180d369162ef08cb8',
name: 'blob',
**type: 'image/png'**,
hash: null,
lastModifiedDate: Wed Jul 20 2016 16:12:21 GMT+0300 (EEST),
_writeStream:
WriteStream {
... },
writable: true,
domain:
Domain {
...
},
_events: {},
_eventsCount: 0,
_maxListeners: undefined,
path: '/tmp/upload_2a4ac9ef22f7156180d369162ef08cb8',
fd: null,
flags: 'w',
mode: 438,
start: undefined,
pos: undefined,
bytesWritten: 1047621,
closed: true }
}
你可以使用这个头文件并手动进行扩展映射(子字符串等)，但也有现成的库。下面两个是我做谷歌搜索时最重要的结果
mime mime类型
它们的用法也很简单:
app.post('/upload2', function (req, res) {
console.log(mime.extension(req.files.image.type));
}
上面的代码片段将把PNG打印到控制台。
试试这个
const path = require('path');
function getExt(str) {
const basename = path.basename(str);
const firstDot = basename.indexOf('.');
const lastDot = basename.lastIndexOf('.');
const extname = path.extname(basename).replace(/(\.[a-z0-9]+).*/i, '$1');
if (firstDot === lastDot) {
return extname;
}
return basename.slice(firstDot, lastDot) + extname;
}
// all are `.gz`
console.log(getExt('/home/charlike/bar/file.gz'));
console.log(getExt('/home/charlike/bar/file.gz~'));
console.log(getExt('/home/charlike/bar/file.gz+cdf2'));
console.log(getExt('/home/charlike/bar/file.gz?quz=zaz'));
// all are `.tar.gz`
console.log(getExt('/home/charlike/bar/file.tar.gz'));
console.log(getExt('/home/charlike/bar/file.tar.gz~'));
console.log(getExt('/home/charlike/bar/file.tar.gz+cdf2'));
console.log(getExt('/home/charlike/bar/file.tar.gz?quz=zaz'));
使用substr()方法比使用split() & pop()方法更有效
在这里看看性能差异:http://jsperf.com/remove-first-character-from-string
// returns: 'html'
var path = require('path');
path.extname('index.html').substr(1);
Update August 2019 As pointed out by @xentek in the comments; substr() is now considered a legacy function (MDN documentation). You can use substring() instead. The difference between substr() and substring() is that the second argument of substr() is the maximum length to return while the second argument of substring() is the index to stop at (without including that character). Also, substr() accepts negative start positions to be used as an offset from the end of the string while substring() does not.
路径。Extname在大多数情况下都可以。但是，它将包括最后一个.之后的所有内容，包括http请求的查询字符串和散列片段:
var path = require('path')
var extname = path.extname('index.html?username=asdf')
// extname contains '.html?username=asdf'
在这种情况下，你可以尝试这样做:
var regex = /[#\\?]/g; // regex of illegal extension characters
var extname = path.extname('index.html?username=asdf');
var endOfExt = extname.search(regex);
if (endOfExt > -1) {
extname = extname.substring(0, endOfExt);
}
// extname contains '.html'
请注意，具有多个句点的扩展(例如.tar.gz)在path.extname下根本不起作用。
