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 + ""
}