Hey there, fellow developer!
As someone who's been around the code block a few times, I've seen JavaScript mature and evolve. Then, along came TypeScript, a statically-typed superset of JavaScript, and it really stirred the pot. Let's dive into this JavaScript vs TypeScript debate and see which one might be the best fit for your needs.

The Age-Old JavaScript

JavaScript is everywhere - from web and mobile apps to servers, APIs, game development, and even IoT devices. It's a dynamic, interpreted language that's been the backbone of web development for years.

let user = { name: "John", age: 30 };

user.sayHi = function() {
  alert("Hello!");
};

user.sayHi(); // Hello!

The dynamism of JavaScript is evident in the above code. We added a function to the user object on the fly, and it just works!

Enter TypeScript

TypeScript, developed and maintained by Microsoft, is a statically typed superset of JavaScript, which means any valid JavaScript code is also valid TypeScript code. It brings static types, interfaces, generics, and other powerful language features to JavaScript.

interface User {
  name: string;
  age: number;

  sayHi(): void;
}

let user: User = {
  name: "John",
  age: 30,

  sayHi() {
    alert("Hello!");
  }
}

user.sayHi(); // Hello!

This TypeScript example uses an interface to enforce a certain structure on the user object. It provides extra assurances about the types being used, catching potential errors early.

When to Use JavaScript or TypeScript

JavaScript is a great choice when you:

• Are creating a small to medium-sized project.
• Need quick prototyping and dynamic typing.
• Are working with a team comfortable with JavaScript but unfamiliar with TypeScript.

TypeScript is a fantastic option when you:

• Are building large-scale applications.
• Require robust type checking, autocompletion, and tooling.
• Work with a team comfortable with statically typed languages like Java or C#.

The Pros and Cons: A Seasoned Perspective

Like every language, both JavaScript and TypeScript have their strengths and weaknesses.

JavaScript

Pros:

• Ubiquity: JavaScript runs everywhere, from browsers to servers.
• Flexibility: Its dynamic nature allows for flexible, on-the-fly coding.
• Community: A huge community means plenty of libraries, frameworks, and learning resources.

Cons:

• Lack of static typing: It's easy to make type-related errors that only surface at runtime.
• Less suitable for large codebases: Without static typing, maintaining large codebases can get tricky.

TypeScript

Pros:

• Type safety: TypeScript's static typing catches errors at compile time, not at runtime.
• Enhanced tooling: Autocomplete, type checking, and advanced refactoring make coding easier.
• Better for large codebases: TypeScript's features make it easier to navigate and maintain large codebases.

Cons:

• Learning curve: If you're not familiar with static typing, there's a bit of a learning curve.
• Compilation step: TypeScript needs to be compiled into JavaScript, adding an extra step to your workflow.

As a senior dev, I'll let you in on a little secret: there's no definitive answer to the JavaScript vs TypeScript debate. It's all about choosing the right tool for the job and the team.

Maybe you're a solo developer working on a personal project with a lot of quick iterations. JavaScript might be your best friend. Or perhaps you're part of a big dev team building a sprawling enterprise app, where TypeScript's robustness could save the day.

Remember, programming languages are just tools in our toolbelt. The key is understanding their strengths and weaknesses and knowing when to use each one.

Good luck, and happy coding!