JavaScript: Reduce an object by the supplied identifiers.

reduce.js

/**
 * Andrew Mead
 *
 * object.reduce(objToMatch)
 *
 * A simple way to return specific properties from an object
 *
 * EXAMPLE
 * var obj = {
 *   name: "andrew",
 *   address: {
 *     street: "Corinthian Ave",
 *     city: "Philadelphia"
 *   };
 *
 * var objToMatch = {
 *   name: true,
 *   address: {
 *     city: true
 *   }
 * };
 *
 * (obj.reduce(objToMatch) == {
 *   name: "andrew",
 *   address: {
 *     city: "Philadelphia"
 *   }
 * })
 *
 * Supported Attributes Values
 *  - true: include attribute. If it is an object, include all chiildren
 *  - false: exclude attribute and children
 *  - undefined: exclude attribute and children
 * */

Object.prototype.reduce = function (map) {
	var obj = this;
	var newObj = {};
	
	// get all properties and nested properties of map that are true
	var props = [];
	function addProps (path) {
		// get all the properties at this level
		// path is 'obj' if it is the objects root
		// path is 'obj.level1.level2' if not the root of object
		var level = eval(path);
		
		if (typeof level == 'object') {
			for (attr in level) {
				if (level.hasOwnProperty(attr) === true) {
					// see if this is a value or nested object
					addProps(path + '.' + attr);
				}
			}
		} else if (eval(level) === false) {
			// ignore that shit!
		} else {
			var tempPath = path.split('.');
			tempPath[0] = 'obj';
			props.push(tempPath.join('.'));
		}
	}
	addProps('map');
	
	// the thing we found in map
	
	// var i;
	// sift through props and copy them from obj into newObj
	for (i = 0; i < props.length; i += 1) {
		var prop = props[i],
			newProp = '';
			
		var temp = prop.split('.');
		temp[0] = 'newObj';
		newProp = temp.join('.');
		
		// check that potentially nested object exist
		var newPropArray = newProp.split('.');
		// loop though
		for (var j = 1; j < newPropArray.length; j += 1) {
			var toCreate = newPropArray.slice(0, j).join('.');
			
			if (toCreate.indexOf('.') === -1) {
			
			} else {
				if (typeof eval(toCreate) == 'undefined') {
					eval(toCreate + '={};');
				}
			}
			
		}
		
		eval(newProp + '=' + prop);
	}
	
	return newObj
};

usage.js

require('./reduce.js');

var obj = {
  _id: 123,
  address: {
    city: 'Philadelphia',
    state: 'PA',
    deep: {
      name: ['andrew', 'mead'],
      age: 21
    }
  }
};

var obj2 = {
  _id: true,
  address: {
    city: false,
    deep: {
      name: true
    }
  }
};

console.log('** reduced object **');
console.log(obj.reduce(obj2));
console.log('** original object **');
console.log(obj);