The difference between JavaScript and TypeScript

JavaScript and TypeScript are two different programming languages ​​that differ in some respects.

1. Type system: JavaScript is a dynamically typed language. The type of a variable is determined at runtime and can be changed at any time. TypeScript introduces a static type system, which can check type errors in code at compile time, providing stricter type checking and type hints.

2. Type annotation: In JavaScript, there is no need to explicitly declare the type of the variable, and it can be assigned directly. In TypeScript, you can use type annotations to explicitly declare the type of variables, such as: `let num: number = 10;`, through type annotations you can specify the type of variables more clearly.

3. ECMAScript standard support: JavaScript is a scripting language based on the ECMAScript standard, and TypeScript is an extension based on JavaScript. TypeScript supports various versions of ECMAScript and adds some additional language features and functionality.

4. Compiler and tool support: JavaScript can run directly in the browser or Node.js environment, while TypeScript needs a compiler to compile TypeScript code into JavaScript code before it can run. TypeScript provides powerful compiler and development tool support, such as type checking, auto-completion, refactoring, etc.

5. Ecosystem: JavaScript has a huge ecosystem, and there are many ready-made third-party libraries and frameworks available. TypeScript can seamlessly use libraries and frameworks in the JavaScript ecosystem and provides additional type declaration files to support type checking.

In short, TypeScript is a superset of JavaScript, which adds a static type system and some new language features to JavaScript, providing a better development experience and code quality assurance. But JavaScript is still a very popular and commonly used language with wide adoption and support. According to specific project requirements and team technology stack, you can choose a suitable language for development.