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

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.

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');
const filename = 'hello.html';
    
path.parse(filename).name;     //=> "hello"
path.parse(filename).ext;      //=> ".html"
path.parse(filename).base; //=> "hello.html"

Further explanation at Node.js documentation page.