Using CodeTree to mutate JavaScript

const codeTree = require("codetree"); let code = ` function sayHelloWorld() { console.log("Hello, World!"); } `; let tree = codeTree.typescript.parse(code); let mutatedTree = codeTree.transformTree( tree, codeTree.typescript.parse("console.log(__);"), matchedTree => codeTree.typescript.parse(`console.error("Hi!");`) ); codeTree.printSource(mutatedTree);