equivalent-exchange

equivalent-exchange

Suchipi's flexible JS/TS codemodding/refactoring toolkit, powered by Babel and Recast.

Features

• Can parse code using modern ES20XX syntax, as well as JSX/TSX and TypeScript/Flow syntax.
• Maintains the source formatting of the original source, where possible; only modified parts of the code will be touched.
• Can generate a source map that maps your input file into your transformed output.

Usage Example

"Transmute" one string of code into another by using the transmute function:

import { transmute } from "equivalent-exchange";

const someJs = "console.log('hi!');";

const result = transmute(someJs, (ast) => {
  // Within this callback, we mutate the AST as desired for the
  // codemod/refactor.
  // Use https://astexplorer.net/ to see what this tree
  // structure looks like!
  ast.program.body[0].expression.callee.arguments[0].value = "goodbye!";
});

console.log(result.code); // console.log("goodbye!");

For more flexible codemods, use the included utilities:

import { transmute, traverse, types } from "equivalent-exchange";

// `traverse` and `types` come from Babel!

const someJs = "console.log('hi!', 'hi again!');";

const result = transmute(someJs, (ast) => {
  // Walk the tree...
  traverse(ast, {
    // And for every StringLiteral node we find...
    StringLiteral(path) {
      const { node } = path;
      // If it starts with 'hi'...
      if (node.value.startsWith("hi")) {
        const newValue = node.value.replace(/^hi/, "bye");
        const newNode = types.stringLiteral(newValue);
        // Change 'hi' to 'bye'
        path.replaceWith(newNode);
      }
    },
  });
});

console.log(result.code); // "console.log('bye!', 'bye again!');"

To transform files in bulk, use the "mapFiles" API:

import { transmute, traverse, types, mapFiles } from "equivalent-exchange";

const results = await mapFiles.fromGlob("src/*.ts", (content, path) => {
  if (path === "src/build-docs.ts") {
    // Skip this file
    return;
  }

  return transmute(content, (ast) => {
    // Walk the tree...
    traverse(ast, {
      // And for every StringLiteral node we find...
      StringLiteral(path) {
        const { node } = path;
        // If it starts with 'hi'...
        if (node.value.startsWith("hi")) {
          const newValue = node.value.replace(/^hi/, "bye");
          const newNode = types.stringLiteral(newValue);
          // Change 'hi' to 'bye'
          path.replaceWith(newNode);
        }
      },
    });
  });
});

API Documentation

See api/index.md.

License

MIT