Dynamical mapper generator by pre-defined template path

getDynamicalMapper.js

const _ = require('lodash');

const template = {
  questionnaireIdToQuestionSeq: {
    '$sections.0.questionData.id$': '01',
    v: {
      '$aaaa.bb.cc$': {
        '$nn.qq.aa$': [
          '$sections.0.questionData.id$',
          '$sections.0.questionData.id$',
          '$sections.1.questionData.id$',
        ],
      }
    },
  },
  question01: {
    questionIds: [
      '$sections.0.questionData.id$',
      '$sections.1.questionData.id$',
    ],
    answerIds: null
  },
}

const traverseMapper = ({
  path = [],
  target = undefined,
  template = target,
  output = _.isArray(target) ? [] : {},
  formatter = value => value,
} = {}) => {
  const handler = ({ template, path, value }) => {
    for(let idx = 0; idx < path.length; idx++) {
      const basePath = path.slice(0, idx + 1);
      const templateType = _.chain(template).get(basePath).isArray().value() ? [] : _.chain(template).get(basePath).isObject().value() ? {} : 'leaf';
      const formattedPath = formatter(basePath);
      if (templateType !== 'leaf') {
        let initValue = _.chain(template).get(basePath).value() || templateType;
        if (_.isArray(initValue)) {
          if (_.chain(output).get(formattedPath).isEmpty().value()) {
            _.chain(output).set(formattedPath, templateType).value();
          }
        } else {
          if (_.chain(output).get(formattedPath).isEmpty().value()) {
            _.chain(output).set(formattedPath, templateType).value();
          }
        }
      } else {
        // array -> push, object -> set directly
        if (_.chain(formattedPath).last().isNumber().value()) {
          _.chain(output).get(formattedPath.slice(0, -1)).push(formatter(value)).value();
        } else {
          _.chain(output).set(formattedPath, formatter(value)).value();
        }
      }
    }
  };
  if (_.isArray(target)) {
    if (_.isEmpty(target)) {
      // empty array: []
      handler({ template, path, value: target });
    } else {
      target.forEach((item, idx) => {
        traverseMapper({ template, path: [...path, idx], target: item, output, formatter });
      });
    }
  } else if (_.isObject(target)) {
    if (_.isEmpty(target)) {
      // empty object: {}
      handler({ template, path, value: target, output });
    } else {
      for (let key in target) {
        traverseMapper({ template, path: [...path, key], target: target[key], output, formatter });
      }
    }
  } else {
    // pure value: string, number, undefined, null
    handler({ template, path, value: target });
  }
  return output;
}

const data = {
  sections: [{questionData: {id: 'scott-id'}}, {questionData: {id: 'scott-id.1'}}],
  aaaa: { bb: { cc: 'scott-cc' } },
  nn: { qq: { aa: 'scott-aa' } },
};

const data2 = {
  sections: [{questionData: {id: 'alan-id'}}, {questionData: {id: 'alan-id.1'}}],
  aaaa: { bb: { cc: 'alan-cc' } },
  nn: { qq: { aa: 'alan-aa' } },
};

const getFormatter = data => (path) => {
  const handler = item => {
    const output = _.isString(item) ? item.replace(/\$/g, '') : item;
      if (output !== item) {
        return _.chain(data).get(output).value();
      }
      return output;
  }
  if (_.isArray(path)) {
    return path.map(item => handler(item));
  }
  return handler(path);
};

const output = _.isArray(template) ? [] : {}
traverseMapper({ target: template, formatter: getFormatter(data), output });
traverseMapper({ target: template, formatter: getFormatter(data2), output });

// unittest
console.log('template:', JSON.stringify(template, null, 2));
console.log();
console.log('output:', JSON.stringify(output, null, 2));

/*
template: {
  "questionnaireIdToQuestionSeq": {
    "$sections.0.questionData.id$": "01",
    "v": {
      "$aaaa.bb.cc$": {
        "$nn.qq.aa$": [
          "$sections.0.questionData.id$",
          "$sections.0.questionData.id$",
          "$sections.1.questionData.id$"
        ]
      }
    }
  },
  "question01": {
    "questionIds": [
      "$sections.0.questionData.id$",
      "$sections.1.questionData.id$"
    ],
    "answerIds": null
  }
}

output: {
  "questionnaireIdToQuestionSeq": {
    "scott-id": "01",
    "v": {
      "scott-cc": {
        "scott-aa": [
          "scott-id",
          "scott-id",
          "scott-id.1"
        ]
      },
      "alan-cc": {
        "alan-aa": [
          "alan-id",
          "alan-id",
          "alan-id.1"
        ]
      }
    },
    "alan-id": "01"
  },
  "question01": {
    "questionIds": [
      "scott-id",
      "scott-id.1",
      "alan-id",
      "alan-id.1"
    ],
    "answerIds": null
  }
}
 */