/*
var list = [
    {id: 1, name:"A"}
]
var oldItem = {id: 1, name:"AAA"}
_.update(list, oldItem);

// → [
    {id: 1, name:"AAA"}
]

var newItem = {id: 2, name:"B"}
_.update(list, newItem);

// → [
    {id: 1, name:"A"},
    {id: 2, name:"B"}
]
*/

(function() {
    'use strict';

    function update(list, item, key) {
        key = key || 'id';
        var listItem = _.find(list, key, item[key]);
        listItem ? _.assign(listItem, item) : list.push(item);

        return list;
    }

    _.mixin({
        'update': update
    });
}());