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:

``ts
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:

`ts
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:

`ts
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