build with tsconfig paths with code examples

Introduction:

TypeScript is a strongly typed programming language that allows developers to write code in a structured manner. It is a superset of JavaScript, which means that it adds additional features to the language. One of the important features that TypeScript brings to the table is the ability to use paths to import modules. Paths are essentially aliases for module paths that help simplify the process of importing files. In this article, we will explore how to build with tsconfig paths with code examples.

Creating a tsconfig file:

The first step in using paths in TypeScript is to create a tsconfig.json file. This file is used to configure the TypeScript compiler. To create this file, execute the following command in the terminal:

tsc --init

This will create a tsconfig.json file in the root directory of your application. The file will have a default configuration that you can modify to suit your needs.

Using paths in the tsconfig file:

To use paths in the tsconfig file, you must first add a paths property to the compilerOptions object in the tsconfig.json file. The paths property takes an object as a value, with each property.

For example, suppose you have a file structure like this:

app/
├── src/
│   ├── components/
│   │   ├── button.tsx
│   │   ├── input.tsx
│   ├── index.ts

To use paths in this scenario, you must first define the root directory of your application using the baseUrl property in the compilerOptions object:

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

The paths property above defines an alias for the components directory. With this alias, you can now import components from the components directory using the alias @components.

For example, to import the button and input components, you can use the following syntax:

import { Button } from '@components/button';
import { Input } from '@components/input';

Using paths in module resolution:

After defining paths in the tsconfig.json file, you need to set the module resolution in the compilerOptions. The module resolution specifies how the compiler should resolve module imports.

The recommended module resolution for using paths is 'Node' as it supports path mappings.

{
  "compilerOptions": {
    //...
    "module": "esnext",
    "moduleResolution": "node",
    "baseUrl": "./",
    "paths": {
      "@components/*": ["src/components/*"]
    }
  }
}

With the module resolution set, you can now use paths when importing files. When importing files, TypeScript first looks for files relative to the current file, then it searches the paths specified in the tsconfig.json file.

Using paths with third-party libraries:

Third-party libraries do not know about your tsconfig.json file. Therefore, you cannot use paths in third-party libraries directly. However, you can use path mapping to create aliases for third-party libraries.

For example, suppose you want to use the lodash library in your application. You can create an alias for lodash using the paths property in the tsconfig.json file:

{
  "compilerOptions": {
    //...
    "baseUrl": "./",
    "paths": {
      "@components/*": ["src/components/*"],
      "lodash": ["node_modules/lodash-es"]
    }
  }
}

With this alias, you can now import lodash using the following syntax:

import _ from 'lodash';

Conclusion:

Paths are a great way to simplify the import process in TypeScript. While it may take some time to set up initially, it can help improve code quality and readability in the long run. In this article, we explored how to build with tsconfig paths with code examples. With the examples provided, you should be well on your way to using paths in your TypeScript application.

Setting baseUrl and paths:

The baseUrl property in the compilerOptions specifies the root directory of the application. All paths specified in the paths property are relative to the baseUrl. Therefore, if you set the baseUrl to "src", then all paths will be relative to the "src" directory.

For example:

{
  "compilerOptions": {
    "baseUrl": "src",
    "paths": {
      "@app/*": ["app/*"],
      "@components/*": ["components/*"]
    }
  }
}

With the configuration above, you can import files from the "app" directory using the "@app" prefix, and files from the "components" directory using the "@components" prefix.

Using Wildcards in Path Mappings:

Wildcard characters can be used in the path mappings to allow for more flexible imports. The "*" character represents any string of characters. For example:

{
  "compilerOptions": {
    "baseUrl": "src",
    "paths": {
      "@app/*": ["app/*"],
      "@components/*": ["components/*"],
      "@utils/*": ["utils/*"],
      "@shared/*": ["components/shared/*"],
      "@types/*": ["types/*"],
      "@constants": ["constants.ts"],
      "*": ["node_modules/*"]
    }
  }
}

With the configuration above, any package installed in the node_modules directory can be imported using wildcards. For example:

import React from "react";
import _ from "lodash";

Setting module resolution:

The module resolution setting in the compilerOptions specifies how the TypeScript compiler should resolve modules. There are two possible values for this setting:

• "classic": This is the default setting and uses the Node.js style of resolving modules (based on the standard Node.js require function).
• "node": This is the recommended setting when using path mappings.

For example:

{
  "compilerOptions": {
    "baseUrl": ".",
    "paths": {
      "@app/*": ["src/app/*"],
      "@components/*": ["src/components/*"]
    },
    "moduleResolution": "node"
  }
}

Using Path Mappings with Jest:

To use path mappings in your Jest test files, you need to add a moduleNameMapper property to your Jest configuration file (jest.config.js):

module.exports = {
  // ...
  moduleNameMapper: {
    "@app/(.*)": "<rootDir>/src/app/$1",
    "@components/(.*)": "<rootDir>/src/components/$1"
  },
  // ...
};

With the configuration above, you can import files from the app directory using the "@app" prefix and files from the components directory using the "@components" prefix in your Jest test files.

Conclusion:

In this article, we've explored how to build with tsconfig paths with code examples. Configuring and using paths in TypeScript can help simplify imports in your codebase and improve readability. By setting the baseUrl and paths properties in your tsconfig.json file, and configuring your module resolution appropriately, you can use path mappings to alias any directory in your project. Importing files from third-party packages is also possible by creating aliases for them. By using wildcards, you can make your path mappings even more flexible. Finally, adding a moduleNameMapper property to your Jest configuration enables you to use path mappings in your test files as well.

Popular questions

1. What is the purpose of using paths in typescript?

Paths are essentially aliases for the module paths that help simplify the process of importing files in TypeScript. By configuring paths in the TypeScript configuration file, developers can replace long relative paths with shorter aliases.

2. How do you set the root directory of your application in tsconfig.json file?

You can set the root directory of your application in the tsconfig.json file with the baseUrl property in the compilerOptions object.

For example:

{
  "compilerOptions": {
    "baseUrl": "src",
    // ...
  },
  // ...
}

In this example, the root directory is set to "src".

3. What is the recommended module resolution for using paths in typescript?

The recommended module resolution for using paths in TypeScript is 'node' as it supports path mappings.

4. Can you use wildcards in path mappings in typescript?

Yes, wildcard characters can be used in the path mappings to allow for more flexible imports. The "*" character represents any string of characters.

For example:

{
  "compilerOptions": {
    "baseUrl": "src",
    "paths": {
      "@app/*": ["app/*"],
      "@components/*": ["components/*"],
      "*": ["node_modules/*"]
    }
  }
}

With the configuration above, any package installed in the node_modules directory can be imported using wildcards.

5. How can you use path mappings in your Jest test files?

To use path mappings in your Jest test files, you need to add a moduleNameMapper property to your Jest configuration file (jest.config.js) and define the path mappings.

For example:

module.exports = {
  // ...
  moduleNameMapper: {
    "@app/(.*)": "<rootDir>/src/app/$1",
    "@components/(.*)": "<rootDir>/src/components/$1"
  },
  // ...
};

With the configuration above, you can use path mappings in your Jest test files to import files from the app and components directories.

Tag

"PathConfigurations"