loDash.js and Underscore.js Mixins

_.compactObject

/**
 * Removes all falsy and undefined values from an object
 * @param  {object} o Object to be compacted
 * @return {object}   Compact Object
 * @link http://stackoverflow.com/a/14058408/417822
 */
_.mixin({'compactObject': function(o) {
	var clone = _.clone(o);

	_.each(clone, function(v, k) {
		if(!v) delete clone[k];
	});

	return clone;
}});

_.getDeep

/**
 * Safely retrieves the value of a deeply nested object value
 * @param  {object} O   The Object to be searched
 * @param  {string} str Dot notation string of the address of the attribute to be retrieved
 * @return {mixed}      Value of nested item or undefined
 * @link http://stackoverflow.com/a/15400575/417822
 */
_.mixin({'getDeep': function(O, str) {
	if ( !_.isObject(O) ) return;

	var seg= str.split('.');
	while(O && seg.length) {
		O = O[seg.shift()];
	}
	return O;
}});

_.hasDeep

/**
 * Tests if a deep value has a value/exists. Uses _.getDeep to retrieve value.
 * @param  {object} O   The Object to be tested
 * @param  {string} str Dot notation string of the address of the attributed to be tested
 * @return {boolean}
 * @todo validate that falesy values 'false' '0' etc come back as true.
 */
_.mixin({'hasDeep': function(O, str) {
	return !_.isUndefined( _.getDeep(O, str) );
}});

_.isDefined

/**
 * Shorthand for !_.isUndefined
 * @param  {mixed} e Item to be tested
 * @return {boolean}
 */
_.mixin({'isDefined': function(e) {
	return !_.isUndefined(e);
}});

_.toggleArray

/**
 * Toggles an array element
 * @param  {Array} arr    Source Array
 * @param  {Mixed} val    Value to toggle
 * @param  {Boolean}      Optional: Boolean to determine whether to add or remove
 * @return {Array}        Result
 */
_.mixin({'arrayToggle': function(arr, val, state) {
  if ( _.indexOf(arr,val)==-1  || state)
  return _.union(arr,[val]);
  else 
    return _.without(arr,val);
}});

Blog Post: http://blog.jstassen.com/2015/09/lodash-js-underscore-js-mixins/