project-references-and-build-optimization

Project References and Build Optimization:

Project references:
Project references enable efficient management of large codebases by dividing the project into smaller, interdependent chunks. Each project can be compiled independently, which streamlines the build process and ensures consistency across the codebase.
- Code Example:
```
// tsconfig.json for a library
{
  "compilerOptions": {
    "composite": true,
    "declaration": true,
    "outDir": "./lib"
  },
  "include": ["src/**/*"]
}
```
Composite projects:
A composite project in TypeScript is configured to reference other projects. This allows for the codebase to be split logically, often by feature or functionality, facilitating easier maintenance and scaling.
- Code Example:
```
// tsconfig.json for the main app
{
  "compilerOptions": {
    "composite": true,
    "outDir": "./dist"
  },
  "references": [
    { "path": "./path-to-library/tsconfig.json" }
  ],
  "include": ["src/**/*"]
}
```
Incremental builds:
Incremental builds compile only the changed files and their dependencies since the last compile, which can significantly reduce build times in larger projects.
- Code Example:
```
// tsconfig.json with incremental enabled
{
  "compilerOptions": {
    "incremental": true,
    "outDir": "./dist"
  },
  "include": ["src/**/*"]
}
```
Build ordering:
In projects with multiple interdependencies, TypeScript determines the correct build order automatically to ensure that dependent projects are built after their dependencies.
- Code Example: No direct code example for this point since build ordering is an internal mechanism of TypeScript's compilation process with composite projects.
OutDir setting:
The outDir setting in tsconfig.json designates where the compiled JavaScript files will be placed. Organizing output directories can help maintain a clear separation between source files and compiled output.
- Code Example:
```
// tsconfig.json with outDir specified
{
  "compilerOptions": {
    "outDir": "./dist"
  },
  "include": ["src/**/*"]
}
```
Declaration maps:
Declaration maps provide a means of tracing back to the original TypeScript source code from the emitted .d.ts files, which is very useful during debugging or when navigating through the code in an editor.
- Code Example:
```
// tsconfig.json with declarationMap enabled
{
  "compilerOptions": {
    "declaration": true,
    "declarationMap": true
  },
  "include": ["src/**/*"]
}
```

Watch mode:
TypeScript's watch mode immediately recompiles your code when it detects changes. This means you get real-time feedback on any errors and can see the results of your changes without having to manually recompile.
- Code Example:
```
Run `tsc --watch` in the terminal within your project directory.
```

Bundling:

Bundling with tools like Webpack can significantly reduce the size of your application by removing unused code and optimizing the modules that are used.

Code Example:

// webpack.config.js example with TypeScript
module.exports = {
  entry: './src/index.ts',
  module: {
    rules: [
      {
        test: /\.tsx?$/,
        use: 'ts-loader',
        exclude: /node_modules/,
      },
    ],
  },
  resolve: {
    extensions: ['.tsx', '.ts', '.js'],
  },
  output: {
    filename: 'bundle.js',
    path: path.resolve(__dirname, 'dist'),
  },
};

Lazy loading:
Dynamic imports can be used to load parts of your application on demand. This can improve the startup time of your application by only loading the code that is necessary for the initial load.
- Code Example:
```
// Lazy loading a module
const module = await import('./module');
```
Exclude unnecessary files:
By excluding files not necessary for your final build, such as tests or development-only scripts, you can speed up the compilation process.
- Code Example:
```
// tsconfig.json with exclude
{
  "exclude": ["node_modules", "**/*.spec.ts"]
}
```
ts-loader / awesome-typescript-loader:
These Webpack loaders enable you to integrate TypeScript compilation into your bundling process, often with improvements like parallel processing.
- Code Example:
```
// webpack.config.js using ts-loader
module: {
  rules: [
    { test: /\.ts$/, loader: 'ts-loader' }
  ]
}
```
NoEmitOnError:
This setting ensures that the TypeScript compiler does not emit output if any errors are detected, helping to prevent the deployment of broken code.
- Code Example:
```
// tsconfig.json with noEmitOnError
{
  "compilerOptions": {
    "noEmitOnError": true
  }
}
```

Path aliases:

Path aliases make import statements cleaner and easier to manage, particularly in large codebases with deeply nested directories.

Code Example:

// tsconfig.json with paths
{
  "compilerOptions": {
    "baseUrl": ".",
    "paths": {
      "@models": ["src/models"],
      "@components/*": ["src/components/*"]
    }
  }
}

Source map optimization:
Disabling source maps for production builds can reduce file sizes and protect your source code.
- Code Example:
```
// tsconfig.json without source maps for production
{
  "compilerOptions": {
    "sourceMap": false
  }
}
```
Linting and formatting:
Linters and formatters can catch many potential problems before they affect the build process, leading to more reliable and maintainable code.
- Code Example:
```
Run `eslint . --ext .ts` to lint your TypeScript files.
```