'use strict'; const { isFunction } = require('../helpers/is'); module.exports = function average(key) { if (key === undefined) { return this.sum() / this.items.length; } if (isFunction(key)) { return new this.constructor(this.items).sum(key) / this.items.length; } return new this.constructor(this.items).pluck(key).sum() / this.items.length; };