Typescript Compiler Tsc And Tsconfigjson

TypeScript Compiler tsc and tsconfigjson Step by step Implementation and Top 10 Questions and Answers

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TypeScript Compiler (`tsc`) and `tsconfig.json`: A Step-by-Step Guide

Introduction to TypeScript

TypeScript (often abbreviated as TS) is a statically typed programming language that is syntactically similar to JavaScript. It adds features such as type declarations, interfaces, enums, and classes, which help developers write robust, maintainable, and scalable code. TypeScript cannot be executed directly by web browsers, so it needs to be compiled into JavaScript—a language that browsers can understand.

What Does TypeScript Add?

Type System: Adds static typing to JavaScript.
Features Not Yet in JavaScript: Classes, modules, interfaces, enumerations, generics, and decorators.
Compilation: Transpiles (converts) TypeScript code into JavaScript.

Understanding TypeScript Compiler (`tsc`)

tsc is the command-line tool provided by Microsoft's TypeScript team to compile .ts files into .js files. Here’s how tsc works:

Installation via npm: TypeScript can be installed globally on your machine using Node Package Manager (npm). Execute the following command in your terminal:
```
npm install -g typescript
```
Basic Compilation: To compile a single TypeScript file to JS, navigate to the directory containing the file and run:
```
tsc filename.ts
```
This command will generate a file named filename.js in the same directory.
Multiple Files: If you have multiple TypeScript files in a project, you can compile all of them at once without specifying individual filenames:
```
tsc
```
When no arguments are passed to tsc, it looks for a configuration file named tsconfig.json in the current directory and compiles files according to the settings defined in this file.

Understanding `tsconfig.json`

The tsconfig.json file sits in the root of a TypeScript project and contains instructions for the TypeScript compiler (tsc). The presence of this file indicates that the folder is the root of a TypeScript project. Here's how to create and use it:

Creating tsconfig.json: You can manually create a tsconfig.json file or use the built-in tsc command to generate the file with default configurations:
```
tsc --init
```
Key Configuration Options: Below are key options you might find or configure in tsconfig.json:
- compilerOptions:
  - target: Specifies the version of ECMAScript to target when compiling TypeScript. Common values include "es5", "es6", "es2017", and "esnext".
```
"target": "ESNext",
```
  - module: Defines what module system TypeScript should use, such as commonjs, es6, amd, etc.
```
"module": "commonjs",
```
  - strict: Enables all strict type-checking options. It's recommended to set this to true for better error-checking.
```
"strict": true,
```
  - outDir: Determines where compiled JS files should be stored. This option helps keep the source files clean.
```
"outDir": "./dist",
```
  - rootDir: Specifies the root directory for input files. This is often used in conjunction with outDir.
```
"rootDir": "./src",
```
  - removeComments: Removes comments from generated JS files.
```
"removeComments": true,
```
  - noEmitOnError: Prevents JS file generation when there are errors.
```
"noEmitOnError": true,
```
  - sourceMap: Generates a corresponding .map file which maps the TypeScript source code to the compiled JavaScript code.
```
"sourceMap": true,
```
  - moduleResolution: Specifies the strategy for resolving modules.
```
"moduleResolution": "node",
```
- include and exclude:
  - include: Lists which files or directories should be included during the compilation.
```
"include": ["src/**/*"],
```
  - exclude: Lists which files or directories should be excluded from the source files list.
```
"exclude": ["node_modules", "**/*.spec.ts"],
```
A Sample Minimal tsconfig.json:
```
{
  "compilerOptions": {
    "target": "ES6",
    "module": "commonjs",
    "strict": true,
    "esModuleInterop": true,
    "skipLibCheck": true,
    "forceConsistentCasingInFileNames": true
  }
}
```
Explanation of the sample config:
- "target": "ES6": Compiles the TypeScript code to ES6.
- "module": "commonjs": Uses CommonJS module system.
- "strict": true : Enforces strong TypeScript rules.
- "esModuleInterop": true : Facilitates interoperability between CommonJS and ES modules.
- "skipLibCheck": true : Skips checking declaration files that come from libraries.
- "forceConsistentCasingInFileNames": true : Ensures consistent casing in imports.
Advanced Configuration Options:
- jsx: Specifies how to compile the JSX syntax. Useful in React projects.
```
"jsx": "react-jsx",
```
- lib: Lists the libraries you want to enable, like DOM manipulation or ES6 features.
```
"lib": ["es6", "dom"],
```
- files: Lists specific TypeScript files to compile, instead of using include/exclude.
```
"files": ["src/file1.ts", "src/file2.ts"]
```
- paths: Specifies how modules are resolved using aliases.
```
"baseUrl": ".",
"paths": {
  "@components/*": ["src/components/*"],
  "@utils/*": ["src/utils/*"]
}
```
- types: Includes additional type definitions.
```
"types": ["jquery", "lodash"]
```
- typeRoots: Specifies the directories to search for type declarations.
```
"typeRoots": ["./node_modules/@types"],
```
Using tsconfig.json: Every time you run tsc in the project root containing tsconfig.json, the compiler uses its settings.
```
tsc
```
If the TypeScript files are correctly formatted, tsc will produce JS files in the specified output directory, apply the specified transformations, and manage the project’s scope according to the configurations.

Practical Usage Scenarios

Below are some examples explaining how tsc and tsconfig.json work together in real-life projects:

React Project: You may need to adjust JSX handling and ensure you're targeting a specific ES version:

{
  "compilerOptions": {
    "target": "ES6",
    "module": "commonjs",
    "strict": true,
    "esModuleInterop": true,
    "jsx": "react-jsx"
  },
  "include": ["src/**/*"],
  "exclude": ["node_modules"]
}

Node.js Backend using TypeScript: In this case, you may want to ensure the use of latest ECMAScript features and commonjs to maintain compatibility with Node.js module system.

{
  "compilerOptions": {
    "target": "ESNext",
    "module": "commonjs",
    "strict": true,
    "esModuleInterop": true,
    "skipLibCheck": true,
    "forceConsistentCasingInFileNames": true
  },
  "include": ["src/**/*"],
  "exclude": ["node_modules"]
}

Angular Frontend: Angular usually uses ES5 syntax and supports various module resolvers, thus the tsconfig.json reflects these specifics:

{
  "compilerOptions": {
    "target": "ES5",
    "module": "es2020",
    "strict": true,
    "esModuleInterop": true
  },
  "include": ["src/**/*.ts"],
  "exclude": ["node_modules", "src/test.ts", "src/**/*.spec.ts"]
}

Conclusion

The TypeScript Compiler (tsc), coupled with tsconfig.json, offers a powerful environment to write, transpile, and manage large-scale applications efficiently. By setting appropriate compiler options in tsconfig.json, developers can control the transpilation process and leverage TypeScript's robust type system fully. As you become more familiar with TypeScript, exploring advanced configuration options will enable you to write code that adheres closely to your project’s standards and practices.

Understanding and effectively configuring tsc and tsconfig.json is essential for leveraging the full potential of TypeScript, ensuring cleaner, more organized, and ultimately more reliable applications.