Convert TypeScript object to JSON. The output file (output-file.json) will be created in the same directory as the input file.

convert-ts-obj-to-json.ts

/**
 * Convert TypeScript object (or JavaScript object) to JSON.
 * 
 * Usage:
 * This code uses Bun for execution, but it can also be run with other tools like Node.js.
 * 
 * Example:
 * bun convert-ts-obj-to-json.ts <input-file.ts>
 * 
 * Note:
 * The output file (output-file.json) will be created in the same directory as the input file.
 */

import * as fs from 'fs';
import * as path from 'path';
import * as ts from 'typescript';

const args = process.argv.slice(2);
if (args.length === 0) {
  console.error('Error: No input file specified.');
  process.exit(1);
}

const inputFilePath = path.resolve(process.cwd(), args[0]);
const outputFilePath = path.join(path.dirname(inputFilePath), path.basename(inputFilePath, '.ts') + '.json');

const convertTsObjectToJson = (inputFile: string, outputFile: string) => {
  if (!fs.existsSync(inputFile)) {
    console.error(`Error: File not found: ${inputFile}`);
    process.exit(1);
  }

  const tsCode = fs.readFileSync(inputFile, 'utf8');
  const sourceFile = ts.createSourceFile(inputFile, tsCode, ts.ScriptTarget.ESNext, true);
  let jsonObject: any = null;

  ts.forEachChild(sourceFile, (node) => {
    if (
      ts.isExportAssignment(node) &&
      ts.isObjectLiteralExpression(node.expression)
    ) {
      jsonObject = extractObject(node.expression);
    }
  });

  if (jsonObject === null) {
    console.error('Error: No object literal found in the input file.');
    process.exit(1);
  }

  fs.writeFileSync(outputFile, JSON.stringify(jsonObject, null, 2), 'utf8');
  console.log(`Converted TypeScript object to JSON: ${outputFile}`);
}

const extractObject = (objectNode: ts.ObjectLiteralExpression): any => {
  const result: any = {};

  objectNode.properties.forEach((prop) => {
    if (ts.isPropertyAssignment(prop) && ts.isIdentifier(prop.name)) {
      const key = prop.name.text;

      if (ts.isObjectLiteralExpression(prop.initializer)) {
        result[key] = extractObject(prop.initializer);
      } else if (ts.isStringLiteral(prop.initializer)) {
        result[key] = prop.initializer.text;
      }
    }
  });

  return result;
}

// main
convertTsObjectToJson(inputFilePath, outputFilePath);