Partial Response Example

partial.js

/*
  
  Use case:

  var map = parseFields('id,name,sub(name)'); 
  var dto = map(obj, map); 

*/

exports.parseFields = function(str) {
  
  var obj = {};
  
  if (!str) {
    return obj;
  }
  
  var re = /(\w+)(\(([\w,]+)\))?,?/g;
  var m;
  
  while ((m = re.exec(str)) != null) {
    var key = m[1];
    if (key) {

      var val = m[3];
      if (val) {
        var vals = val.split(',');
        obj[key] = {};
        for (var i = 0; i < vals.length; i++) {
          obj[key][vals[i]] = true;
        };
      } else {
        obj[key] = true;
      }
    }
  }

  return obj;
};

exports.map = function(obj, map, seen) {

  if (typeof obj !== 'object' ||
    obj === null) {

    return obj;
  }

  seen = seen || {
    orig: [],
    copy: []
  };

  var lookup = seen.orig.indexOf(obj);
  if (lookup !== -1) {
    return seen.copy[lookup];
  }

  var newObj;
  var cloneDeep = false;

  if (!Array.isArray(obj)) {
    if (Buffer.isBuffer(obj)) {
      newObj = Buffer.from(obj);
    } else if (obj instanceof Date) {
      newObj = new Date(obj.getTime());
    } else if (obj instanceof RegExp) {
      newObj = new RegExp(obj);
    } else {
      var proto = Object.getPrototypeOf(obj);
      if (!proto || proto.isImmutable) {
        newObj = obj;
      } else {
        newObj = Object.create(proto);
        cloneDeep = true;
      }
    }
  } else {
    newObj = [];
    cloneDeep = true;
  }

  seen.orig.push(obj);
  seen.copy.push(newObj);

  if (cloneDeep) {
    for (var i in obj) {
      if (obj.hasOwnProperty(i)) {
        var descriptor = Object.getOwnPropertyDescriptor(obj, i);
        if (descriptor.get || descriptor.set) {
          Object.defineProperty(newObj, i, descriptor);
        } else {

          var subMap;
          var doMap = true;

          if (Array.isArray(obj)) {
            subMap = map;
          }
          else if (map && map[i]) {
            subMap = (map && (typeof map[i] === 'object')) ? map[i] : null
          }
          else if (map) {
            doMap = false;
          }

          if (doMap) {
            newObj[i] = exports.map(obj[i], subMap, seen);
          }
        }
      }
    }
  }

  return newObj;
};