Observable Arrays

和对象相似，使用observable也可以使数组变成可观察的，其还是通过递归工作实现的，所以所有（将来有）的数组值都是可被观察的。

import {observable, autorun} from "mobx";

var todos = observable([
    { title: "Spoil tea", completed: true },
    { title: "Make coffee", completed: false }
]);

autorun(() => {
    console.log("Remaining:", todos
        .filter(todo => !todo.completed)
        .map(todo => todo.title)
        .join(", ")
    );
});
// Prints: 'Remaining: Make coffee'

todos[0].completed = false;
// Prints: 'Remaining: Spoil tea, Make coffee'

todos[2] = { title: 'Take a nap', completed: false };
// Prints: 'Remaining: Spoil tea, Make coffee, Take a nap'

todos.shift();
// Prints: 'Remaining: Make coffee, Take a nap'

由于 ES5 中原生数组的限制（array.observe仅在 ES7 中可用, 并且数组无法扩展），observable将参数提供的数组进行克隆替代原始的那个。在实践中，这些数组工作的和原生的数组一样好，并且其支持所有原生方法，包括索引分配，up-to 和包括数组的长度。

Bear in mind however that Array.isArray(observable([])) will yield false, so whenever you need to pass an observable array to an external library, it is a good idea to create a shallow copy before passing it to other libraries or built-in functions (which is good practice anyway) by using array.slice(). In other words, Array.isArray(observable([]).slice()) will yield true.

Unlike the built-in implementation of the functions sort and reverse, observableArray.sort and reverse will not change the array in-place, but only will return a sorted / reversed copy.

Besides all built-in functions, the following goodies are available as well on observable arrays:

• intercept(interceptor). Can be used to intercept any change before it is applied to the array. See observe & intercept
• observe(listener, fireImmediately? = false) Listen to changes in this array. The callback will receive arguments that express an array splice or array change, conforming to ES7 proposal. It returns a disposer function to stop the listener.
• clear() Remove all current entries from the array.
• replace(newItems) Replaces all existing entries in the array with new ones.
• find(predicate: (item, index, array) => boolean, thisArg?, fromIndex?) Basically the same as the ES7 Array.find proposal, except for the additional fromIndex parameter.
• remove(value) Remove a single item by value from the array. Returns true if the item was found and removed.
• peek() Returns an array with all the values which can safely be passed to other libraries, similar to slice(). In contrast to slice, peek doesn't create a defensive copy. Use this in performance critical applications if you know for sure that you use the array in a read-only manner. In performance critical sections it is recommended to use a flat observable array as well.