redeyed

What is redeyed?

The redeyed npm package provides functionality for syntax highlighting and code transformation by allowing modifications to JavaScript code through configuration of hooks for tokens and types. It enables parsing JavaScript code, identifying tokens and their types, and then applying transformations or highlighting based on the configuration provided.

What are redeyed's main functionalities?

Syntax Highlighting

This feature allows for syntax highlighting of JavaScript code. By configuring the `String` token, all string literals in the code can be highlighted. The example demonstrates how to highlight string literals in green using ANSI escape codes.

const redeyed = require('redeyed');
const config = {
  String: {
    _default: { open: '\x1b[32m', close: '\x1b[39m', _default: true }
  }
};
const code = '"Hello, world!"';
const highlighted = redeyed(code, config).code;
console.log(highlighted);

Code Transformation

This feature enables code transformation by applying custom transformations to specific JavaScript tokens. In the example, all instances of the `function` keyword are prefixed with `_function_`, demonstrating a simple transformation.

const redeyed = require('redeyed');
const config = {
  Keyword: {
    'function': { open: '_function_', close: '' }
  }
};
const code = 'function example() {}';
const transformed = redeyed(code, config).code;
console.log(transformed);

Other packages similar to redeyed

esprima

Esprima is a popular JavaScript parser that provides a detailed syntax tree of JavaScript code. While it doesn't directly offer syntax highlighting or transformation, it serves as a foundation for building such tools. Compared to redeyed, Esprima offers more in-depth analysis but requires more setup for syntax highlighting or code transformation.

jscodeshift

jscodeshift is a toolkit for running codemods over multiple JavaScript or TypeScript files. It uses a different approach than redeyed by focusing on code transformations rather than syntax highlighting. jscodeshift offers a more comprehensive API for complex code modifications, making it more suitable for large-scale refactoring.

highlight.js

highlight.js is a syntax highlighter written in JavaScript. It supports a wide range of programming languages, including JavaScript. Unlike redeyed, which allows for dynamic modification of code through configuration, highlight.js focuses solely on syntax highlighting without the ability to transform code.

README

redeyed

Add color to your JavaScript!

Red Eyed Tree Frog (Agalychnis callidryas)

What?

Takes JavaScript code, along with a config and returns the original code with tokens wrapped and/or replaced as configured.

What for?

One usecase is adding metadata to your code that can then be used to apply syntax highlighting.

How?

• copy the config.js and edit it in order to specify how certain tokens are to be surrounded/replaced
• replace the undefined of each token you want to configure with one of the following

{String} config

'before:after': wraps the token inside before/after

{Object} config

{ _before: 'before', _after: 'after' }: wraps token inside before/after

{Function} config

function (s) { return 'replacement for s'; }: replaces the token with whatever is returned by the provided function

Missing before and after resolution

For the {String} and {Object} configurations, 'before' or 'after' may be omitted:

• {String}:
  • 'before:' (omitting 'after')
  • ':after' (omitting 'before')
• {Object}:
  • { _before: 'before' } (omitting '_after')
  • { _after: 'after' } (omitting '_before')

In these cases the missing half is resolved as follows:

• from the parent._default (i.e., Keyword._default) if found
• otherwise from the config._default if found
• otherwise '' (empty string)

Transforming JavaScript code

Invoke redeyed with your configuration and a code snippet as in the below example:

var redeyed = require('redeyed')
  , config = require('./path/to/config')
  , code = 'var a = 3;'
  , result;

// redeyed will throw an error (caused by the esprima parser) if the code has invalid javascript
try {
  result = redeyed(code, config);
  console.log(result);
} catch(err) {
  console.error(err);
}

redeyed in the wild

• cardinal: Syntax highlights JavaScript code with ANSI colors to be printed to the terminal