Javascript:
Javascript comes with a huge ecosystem of frameworks and libraries. It follows the document object model and is great for web applications. However, the language is less performant on highly complex use cases and dynamic typing often leads to runtime errors. Javascript can be used for both frontend and backend. Unfortunately, it is only really good for single-threaded use cases. It supports object-orientation, cross-platform development, and asynchronous programming like callbacks, promises, and async/wait.
Dart:
Dart is a strongly typed language that is useful for cross-platform mobile applications and server-side that require more structure, static typing, and performance. Similar to Javascript, it is object-oriented, useful for cross-platform development, and provides asynchronous programming mechanisms. Unfortunately, it significantly lags behind in the community with a smaller ecosystem. However, this is likely to grow rapidly due to Flutter.
Use Dart for your next mobile app or game. The learning curve for Dart is relatively high because of a smaller community. Use Javascript if you rely on a larger ecosystem and would rather not reinvent the wheel.
