How to use the command 'lebab' (with examples)

The lebab command is a JavaScript modernizer that transpiles code to ES6/ES7. It provides various transformations to upgrade your JavaScript code to the latest standards. This article will illustrate several use cases of the lebab command, along with their code, motivations, explanations, and example outputs.

Use case 1: Display a list of the available transformations

Code:

lebab --help

Motivation: The lebab command offers a range of transformations to modernize your JavaScript code. To know which transformations are available, it is useful to display a list of them.

Explanation: The --help option displays a list of available transformations supported by lebab. This command does not require any additional arguments.

Example output:

Available transformations:
  arrow => Replace function expressions with arrow functions
  lets => Replace `var` with `let` and `const`
  template => Replace string concatenation with template strings
  ... (more transformations)

Use case 2: Transpile using one or more comma-separated transformations

Code:

lebab --transform transformation

Motivation: In some cases, you may want to selectively apply specific transformations to your JavaScript code. The lebab command allows you to specify one or more transformations using the --transform option.

Explanation: The --transform option followed by a comma-separated list of transformations instructs lebab to apply the specified transformations during the transpilation process. You need to replace transformation with the actual name of the desired transformation.

Example output:

Transpiling code using the 'arrow' transformation:
arrow.js --> arrowResult.js

Use case 3: Transpile a file to stdout

Code:

lebab path/to/input_file

Motivation: Sometimes, you may want to transpile a JavaScript file and output the result to the console (stdout). This can be helpful if you want to preview the transpiled code without writing it to a file.

Explanation: By providing the path/to/input_file argument, lebab transpiles the specified file and prints the transpiled code to the console (stdout).

Example output:

Transpiling 'input.js' to 'stdout':
Original code:
function oldFormat() {
  return "Hello, world!";
}

Transpiled code:
const newFormat = () => {
  return "Hello, world!";
};

Use case 4: Transpile a file to the specified output file

Code:

lebab path/to/input_file --out-file path/to/output_file

Motivation: If you want to transpile a JavaScript file and save the result to a specific output file, you can use the --out-file option. This allows you to easily update your codebase with the latest JavaScript syntax.

Explanation: By providing both the path/to/input_file and path/to/output_file arguments, lebab transpiles the specified input file and saves the transpiled code to the specified output file.

Example output:

Transpiling 'input.js' to 'output.js':
Original code in 'input.js':
function oldFormat() {
  return "Hello, world!";
}

Transpiled code saved to 'output.js':
const newFormat = () => {
  return "Hello, world!";
};

Use case 5: Replace all .js files in-place in the specified directory, glob, or file

Code:

lebab --replace directory|glob|file

Motivation: Instead of manually transpiling each JavaScript file individually, you can efficiently upgrade multiple files by utilizing the --replace option. This option replaces all .js files in a directory, glob pattern, or specific file with their transpiled versions.

Explanation: The --replace option followed by directory, glob pattern, or specific file allows lebab to find all JavaScript files matching the given pattern or file and replace them in-place with their transpiled versions.

Example output:

Replacing all JavaScript files in the 'src' directory:
Original code in 'src/main.js':
function oldFormat() {
  return "Hello, world!";
}

Transpiled code saved in 'src/main.js':
const newFormat = () => {
  return "Hello, world!";
};

Original code in 'src/utils.js':
var pi = 3.14159;

Transpiled code saved in 'src/utils.js':
const pi = 3.14159;

Conclusion:

The lebab command provides a convenient way to transpile JavaScript code to the latest ES6/ES7 standards by applying various transformations. Whether you want to preview the transpiled code, save it to a specific file, or upgrade multiple files in one go, the lebab command offers flexible options to meet your needs.