The syntax of JavaScript does not suit everyone’s needs. Different people want different features.
That’s to be expected, because projects and requirements are different for everyone.
So recently a plethora of new languages appeared, which are transpiled (converted) to JavaScript before they run in the browser.
Modern tools make the transpilation very fast and transparent, actually allowing developers to code in another language and auto-converting it “under the hood”.
Examples of such languages:
CoffeeScript is a “syntactic sugar” for JavaScript. It introduces shorter syntax, allowing us to write clearer and more precise code. Usually, Ruby devs like it. TypeScript is concentrated on adding “strict data typing” to simplify the development and support of complex systems. It is developed by Microsoft. Flow also adds data typing, but in a different way. Developed by Facebook. Dart is a standalone language that has its own engine that runs in non-browser environments (like mobile apps), but also can be transpiled to JavaScript. Developed by Google.