TypeScript is becoming increasingly popular among developers due to its ability to add static types to JavaScript, enabling better code organization, bug prevention, and code navigation. In order to convert TypeScript code into plain JavaScript, the TypeScript compiler (tsc) comes into play. This command-line tool provides various options and features that can help developers during the compilation process. In this article, we will explore different use cases of the tsc command with code examples to illustrate their functionalities.

Use Case 1: Compiling a TypeScript file into JavaScript

tsc foobar.ts

Motivation:

This use case is to convert a single TypeScript file (foobar.ts) into its equivalent JavaScript file (foobar.js), which can be executed directly in the browser or Node.js environment.

Explanation:

• tsc: This is the command to invoke the TypeScript compiler.
• foobar.ts: This is the input TypeScript file that needs to be compiled.

Example Output:

The foobar.ts file will be compiled into foobar.js. If there are no syntax or type errors, a new foobar.js file will be created with the equivalent JavaScript code.

Use Case 2: Specifying the ECMAScript target syntax

tsc --target ES5|ES2015|ES2016|ES2017|ES2018|ESNEXT foobar.ts

Motivation:

Sometimes, it is required to specify the target ECMAScript version for which the TypeScript code should be compiled. This can be useful when targeting specific environments or taking advantage of the latest JavaScript features.

Explanation:

• --target ES5|ES2015|ES2016|ES2017|ES2018|ESNEXT: This flag sets the ECMAScript version to which TypeScript code will be compiled. Choose one of the available options to designate the desired target syntax.
• foobar.ts: This is the input TypeScript file that needs to be compiled.

Example Output:

The foobar.ts file will be compiled into JavaScript, adhering to the specified ECMAScript target version.

Use Case 3: Specifying the name of the output JavaScript file

tsc --outFile output.js input.ts

Motivation:

By default, the TypeScript compiler generates an output JavaScript file with the same name as the input TypeScript file. However, there may be cases where you want to specify a custom name for the output file.

Explanation:

• --outFile output.js: This flag sets the name of the output JavaScript file to be generated by the TypeScript compiler.
• input.ts: This is the input TypeScript file that needs to be compiled.

Example Output:

The input.ts file will be compiled into JavaScript and saved as output.js.

Use Case 4: Compiling a TypeScript project defined in a tsconfig.json file

tsc --build tsconfig.json

Motivation:

In larger TypeScript projects, it is common to have a tsconfig.json file that specifies compiler options and includes a list of files to compile. Using this tsconfig.json file, we can compile the entire project with a single command.

Explanation:

• --build tsconfig.json: This flag tells the TypeScript compiler to compile the project defined in the tsconfig.json file.

Example Output:

The TypeScript compiler will read the configuration from tsconfig.json and compile all the TypeScript files specified in the project.

Use Case 5: Using command-line options and arguments fetched from a text file

tsc @args.txt

Motivation:

When the number of command-line options and arguments becomes large and complex, specifying them directly on the command line can make it difficult to read and maintain. By using a text file to fetch the options and arguments, we can manage them more easily.

Explanation:

• @args.txt: This syntax allows the TypeScript compiler to read command-line options and arguments from a text file (args.txt).

Example Output:

The TypeScript compiler will read and process the command-line options and arguments specified in the args.txt file.

Use Case 6: Type-checking multiple JavaScript files and outputting only errors

tsc --allowJs --checkJs --noEmit src/**/*.js

Motivation:

In many projects, there can be a mixture of TypeScript and JavaScript files. By enabling type-checking for JavaScript files and suppressing the emission of JavaScript output, we can capture potential errors in those files without generating any output.

Explanation:

• --allowJs: This flag enables the TypeScript compiler to process JavaScript files along with TypeScript files.
• --checkJs: This flag instructs the TypeScript compiler to perform type-checking on JavaScript files.
• --noEmit: This flag prevents the TypeScript compiler from emitting JavaScript output.
• src/**/*.js: This is the glob pattern representing the target JavaScript files to be type-checked.

Example Output:

The TypeScript compiler will analyze the specified JavaScript files, perform type-checking, and output any errors found in those files without generating any JavaScript output.

Conclusion

In this article, we explored different use cases of the TypeScript compiler (tsc) command. We demonstrated how to compile TypeScript files into JavaScript, set the ECMAScript target syntax, specify the output JavaScript file name, and compile a TypeScript project defined in a tsconfig.json file. Additionally, we covered using command-line options and arguments fetched from a text file and how to type-check multiple JavaScript files, outputting only errors. By understanding and utilizing these various options, developers can efficiently compile and validate their TypeScript projects before deploying them.