How to trim a file extension from a String in JavaScript?
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27-09-2019 - |
Question
For example, assuming that x = filename.jpg
, I want to get filename
, where filename
could be any file name (Let's assume the file name only contains [a-zA-Z0-9-_] to simplify.).
I saw x.substring(0, x.indexOf('.jpg'))
on DZone Snippets, but wouldn't x.substring(0, x.length-4)
perform better? Because, length
is a property and doesn't do character checking whereas indexOf()
is a function and does character checking.
Solution
If you know the length of the extension, you can use x.slice(0, -4)
(where 4 is the three characters of the extension and the dot).
If you don't know the length @John Hartsock regex would be the right approach.
If you'd rather not use regular expressions, you can try this (less performant):
filename.split('.').slice(0, -1).join('.')
Note that it will fail on files without extension.
OTHER TIPS
Not sure what would perform faster but this would be more reliable when it comes to extension like .jpeg
or .html
x.replace(/\.[^/.]+$/, "")
In node.js, the name of the file without the extension can be obtained as follows.
const path = require('path');
var filename = 'hello.html';
path.parse(filename).name; // hello
path.parse(filename).ext; // .html
Further explanation at Node.js documentation page.
x.length-4
only accounts for extensions of 3 characters. What if you have filename.jpeg
or filename.pl
?
EDIT:
To answer... sure, if you always have an extension of .jpg
, x.length-4
would work just fine.
However, if you don't know the length of your extension, any of a number of solutions are better/more robust.
x = x.replace(/\..+$/, '');
OR
x = x.substring(0, x.lastIndexOf('.'));
OR
x = x.replace(/(.*)\.(.*?)$/, "$1");
OR (with the assumption filename only has one dot)
parts = x.match(/[^\.]+/);
x = parts[0];
OR (also with only one dot)
parts = x.split(".");
x = parts[0];
You can perhaps use the assumption that the last dot will be the extension delimiter.
var x = 'filename.jpg';
var f = x.substr(0, x.lastIndexOf('.'));
If file has no extension, it will return empty string. To fix that use this function
function removeExtension(filename){
var lastDotPosition = filename.lastIndexOf(".");
if (lastDotPosition === -1) return filename;
else return filename.substr(0, lastDotPosition);
}
In Node.js versions prior to 0.12.x:
path.basename(filename, path.extname(filename))
Of course this also works in 0.12.x and later.
This works, even when the delimiter is not present in the string.
String.prototype.beforeLastIndex = function (delimiter) {
return this.split(delimiter).slice(0,-1).join(delimiter) || this + ""
}
"image".beforeLastIndex(".") // "image"
"image.jpeg".beforeLastIndex(".") // "image"
"image.second.jpeg".beforeLastIndex(".") // "image.second"
"image.second.third.jpeg".beforeLastIndex(".") // "image.second.third"
Can also be used as a one-liner like this:
var filename = "this.is.a.filename.txt";
console.log(filename.split(".").slice(0,-1).join(".") || filename + "");
EDIT: This is a more efficient solution:
String.prototype.beforeLastIndex = function (delimiter) {
return this.substr(0,this.lastIndexOf(delimiter)) || this + ""
}
I like this one because it is a one liner which isn't too hard to read:
filename.substring(0, filename.lastIndexOf('.')) || filename
This can also be done easily with path using the basename and extname methods.
const path = require('path')
path.basename('test.txt', path.extname('test.txt'))
I don't know if it's a valid option but I use this:
name = filename.split(".");
// trimming with pop()
name.pop();
// getting the name with join()
name.join('.'); // we split by '.' and we join by '.' to restore other eventual points.
It's not just one operation I know, but at least it should always work!
UPDATE: If you want a oneliner, here you are:
(name.split('.').slice(0, -1)).join('.')
Another one-liner:
x.split(".").slice(0, -1).join(".")
Here's another regex-based solution:
filename.replace(/\.[^.$]+$/, '');
This should only chop off the last segment.
The accepted answer strips the last extension part only (.jpeg
), which might be a good choice in most cases.
I once had to strip all extensions (.tar.gz
) and the file names were restricted to not contain dots (so 2015-01-01.backup.tar
would not be a problem):
var name = "2015-01-01_backup.tar.gz";
name.replace(/(\.[^/.]+)+$/, "");
Simple one:
var n = str.lastIndexOf(".");
return n > -1 ? str.substr(0, n) : str;
If you have to process a variable that contains the complete path (ex.: thePath = "http://stackoverflow.com/directory/subdirectory/filename.jpg"
) and you want to return just "filename" you can use:
theName = thePath.split("/").slice(-1).join().split(".").shift();
the result will be theName == "filename";
To try it write the following command into the console window of your chrome debugger:
window.location.pathname.split("/").slice(-1).join().split(".").shift()
If you have to process just the file name and its extension (ex.: theNameWithExt = "filename.jpg"
):
theName = theNameWithExt.split(".").shift();
the result will be theName == "filename", the same as above;
Notes:
- The first one is a little bit slower cause performes more operations; but works in both cases, in other words it can extract the file name without extension from a given string that contains a path or a file name with ex. While the second works only if the given variable contains a filename with ext like filename.ext but is a little bit quicker.
- Both solutions work for both local and server files;
But I can't say nothing about neither performances comparison with other answers nor for browser or OS compatibility.
working snippet 1: the complete path
var thePath = "http://stackoverflow.com/directory/subdirectory/filename.jpg";
theName = thePath.split("/").slice(-1).join().split(".").shift();
alert(theName);
working snippet 2: the file name with extension
var theNameWithExt = "filename.jpg";
theName = theNameWithExt.split("/").slice(-1).join().split(".").shift();
alert(theName);
working snippet 2: the file name with double extension
var theNameWithExt = "filename.tar.gz";
theName = theNameWithExt.split("/").slice(-1).join().split(".").shift();
alert(theName);
var fileName = "something.extension";
fileName.slice(0, -path.extname(fileName).length) // === "something"
Though it's pretty late, I will add another approach to get the filename without extension using plain old JS-
path.replace(path.substr(path.lastIndexOf('.')), '')
This is where regular expressions come in handy! Javascript's .replace()
method will take a regular expression, and you can utilize that to accomplish what you want:
// assuming var x = filename.jpg or some extension
x = x.replace(/(.*)\.[^.]+$/, "$1");
Another one liner - we presume our file is a jpg picture >> ex: var yourStr = 'test.jpg';
yourStr = yourStr.slice(0, -4); // 'test'
You can use path
to maneuver.
var MYPATH = '/User/HELLO/WORLD/FILENAME.js';
var MYEXT = '.js';
var fileName = path.basename(MYPATH, MYEXT);
var filePath = path.dirname(MYPATH) + '/' + fileName;
Output
> filePath
'/User/HELLO/WORLD/FILENAME'
> fileName
'FILENAME'
> MYPATH
'/User/HELLO/WORLD/FILENAME.js'
x.slice(0, -(x.split('.').pop().length + 1));
This is the code I use to remove the extension from a filename, without using either regex or indexOf (indexOf is not supported in IE8). It assumes that the extension is any text after the last '.' character.
It works for:
- files without an extension: "myletter"
- files with '.' in the name: "my.letter.txt"
- unknown length of file extension: "my.letter.html"
Here's the code:
var filename = "my.letter.txt" // some filename
var substrings = filename.split('.'); // split the string at '.'
if (substrings.length == 1)
{
return filename; // there was no file extension, file was something like 'myfile'
}
else
{
var ext = substrings.pop(); // remove the last element
var name = substrings.join(""); // rejoin the remaining elements without separator
name = ([name, ext]).join("."); // readd the extension
return name;
}
I would use something like x.substring(0, x.lastIndexOf('.')). If you're going for performance, don't go for javascript at all :-p No, one more statement really doesn't matter for 99.99999% of all purposes.