How to trim a file extension from a String in JavaScript?

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 nam

Answer 1

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 + ""
}

Answer 2

Here's another regex-based solution:

filename.replace(/\.[^.$]+$/, '');

This should only chop off the last segment.

Answer 3

I like this one because it is a one liner which isn't too hard to read:

filename.substring(0, filename.lastIndexOf('.')) || filename

Answer 4

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.

Answer 5

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.