Flatten JavaScript Objects

flatten.js

// delimter to join flattened keys
var delimiter = ' '

/*
 * Flattens an object
 * @param {object} object - object to flatten
 * @param {boolean} shallow - if true object is only flattened one level
 * @return {object} - flattened object
 */
function flatten(object, shallow) {
  var flattened = {},
    property,
    value,
    nextLevel,
    prefix;

  for(property in object) {
    value = object[property];

    if(typeof value === 'object' && shallow !== null && value !== null) {

      // if shallow is required, set shallow to stopping keyword null
      if(shallow) shallow = null;

      nextLevel = flatten(value, shallow);
      prefix = property + delimiter;

      merge(flattened, nextLevel, prefix);

    } else {
      flattened[property] = value;
    }
  }

  return flattened;
}

/*
 * Destructively merges source data to an object
 * @param {object} object - object to merge data into
 * @param {object} source - object of source data
 * @param {string} prefix - [optional] prefix properties with value
 */
function merge(object, source, prefix) {
  var merged = {},
    property,
    value;

  prefix = prefix || '';

  for(property in source) {
    value = source[property];

    object[prefix + property] = value;
  }

  return object;
}


/*
 * Examples
 */

// flatten an object with depth
var object = {1: {2: 3}};

flatten(object);
// => { '1 2': 3 }


// flatten a more complex object
var object = {
  1: {
    2: 3,
    4: {5: 6},
    7: {8: 9, 10: 11}
  },
  12: 13
};

flatten(object);
// => { '12': 13, '1 2': 3, '1 4 5': 6, '1 7 8': 9, '1 7 10': 11 }


// flatten an object with the shallow flag
var object = {
  1: {
    2: 3,
    4: {5: 6},
    7: {8: 9, 10: 11}
  },
  12: 13
};

flatten(object, true);
// => { '12': 13,
//      '1 2': 3,
//      '1 4': { '5': 6 },
//      '1 7': { '8': 9, '10': 11 } }


// flatten an object with non-plain-object values
var object = {
  1: {
    2: null,
    3: ['a', 'b', 'c'],
  },
};

flatten(object);
// => { '1 2': null, '1 3 0': 'a', '1 3 1': 'b', '1 3 2': 'c' }
// note: arrays are flattened using their indices as property names
// this is the intended action