reverse-source-map.js

const fs = require("fs");
const { SourceMapConsumer, SourceMapGenerator } = require("source-map");

function reverseSourceMap(sourceMap) {
  return SourceMapConsumer.with(sourceMap, null, (consumer) => {
    const reversedMap = new SourceMapGenerator();
    consumer.eachMapping((mapping) => {
      reversedMap.addMapping({
        generated: {
          line: mapping.originalLine,
          column: mapping.originalColumn,
        },
        original: {
          line: mapping.generatedLine,
          column: mapping.generatedColumn,
        },
        source: "deobfuscated.js",
      });
    });
    return reversedMap.toJSON();
  });
}

const sourceMap = JSON.parse(fs.readFileSync(process.argv[2], "utf-8"));

reverseSourceMap(sourceMap).then((reverseMap) =>
  console.log(JSON.stringify(reverseMap, null, 2))
);