Meet the Hypermod Editor

export default function transform(file, { j }) {
  const ast = j(file.source);

  const leftPadImports = ast.find(j.ImportDeclaration, {
    source: { value: "left-pad" },
  });

  const leftPadLocalName = getSpecifierName(
    leftPadImports.find(j.ImportDefaultSpecifier)
  );

  leftPadImports.remove();

  ast
    .find(j.CallExpression, { callee: { name: leftPadLocalName } })
    .forEach((callPath) => {
      const args = callPath.node.arguments;

      if (args.length >= 2) {
        const stringArg = args[0];
        const targetLength = args[1];
        const padString = args.length > 2 ? args[2] : j.literal(" ");

        j(callPath).replaceWith(
          j.callExpression(
            j.memberExpression(stringArg, j.identifier("padStart")),
            [targetLength, padString]
          )
        );
      }
    });

  return ast.toSource();
}

function getSpecifierName(specifiers) {
  if (!specifiers.length) return null;
  return specifiers.nodes()[0].local.name;
}