Introduction to TypeScript

• TypeScript is a subset of JavaScript. TypeScript code is compiled into JavaScript code. TypeScript = JavaScript + Additional Features.
• TypesScript files are saved with .ts. extension.
• Any valid .js file can be renamed to .ts.
• Compiled TypeScript can be consumed from any JavaScript code.
• It is pure Object Oriented Language like C# or Java with classes, objects, interfaces, inheritance etc.
• To learn TypeScript, you should have basic knowledge of JavaScript and Object Oriented concepts.
• TypeScript is portable across browsers, devices and operating systems. It can run on any environment where JavaScript can run.
• TypeScript provides with error-checking feature. It compiles the code and generate compilation error, if there are any syntax errors.
• TypeScript is strongly typed script. Variable declared with no type can be inferred by TLS (TypeScript Language Service) based on its value.
• TypeScript also supports  type definition for existing JavaScript libraries. TypeScript Definition file, .d.ts extension, provides definition for external JavaScript libraries.
• When TypeScript is compiled, there is an option to create a declaration fie, which functions as an interface to the components in the compiled JavaScript.
• Declaration files are similar to header files in C++.

Components of TypeScript

• Language: It has syntax, keywords and type annotations.
• TypeScript Compiler: TypeScript Compiler (TSC) converts the TypeScript code into JavaScript.
• TypeScript Language Service: It exposes an additional layer around the core compiler pipeline that are editor-like applications.