code: function add(obj, path, value, i) {
  	i = i || 0
  
  	var key = path[i],
  		last = i === path.length - 1
  
  	if (!obj || typeof obj !== 'object') {
  		throw new Error('Can\'t add key ' + key + ' to non-object')
  	}
  
  	if (Array.isArray(obj)) {
  		if (typeof key !== 'number') {
  			obj.forEach(function (each) {
  				add(each, path, value, i)
  			})
  		} else if (key >= 0 && key <= obj.length) {
  			if (last) {
  				obj[key] = value
  			} else {
  				add(obj[key], path, value, i + 1)
  			}
  		} else {
  			throw new Error('Can\'t add index ' + key + ' to an array with ' + obj.length + ' elements')
  		}
  	} else {
  		if (typeof key !== 'string') {
  			throw new Error('Can\'t add the numeric key ' + key + ' to an object')
  		} else {
  			if (last) {
  				obj[key] = value
  			} else {
  				if (!(key in obj)) {
  					obj[key] = Object.create(null)
  				}
  				add(obj[key], path, value, i + 1)
  			}
  		}
  	}
  }
docs: Add/update a path off an object
  @param {!Object} obj
  @param {*} value
  @param {Array<string|number>} path
  @param {number} [i]
  @throws {Error}
  @private