使用JavaScript观察对象更改

Watching for changes to an object's property has always been a much sought after task; many shims have been used over the years to listen to object changes.  These days we have better methods for listening to object changes:  the Proxy API.  Sindre Sorhus has created on-change, a tiny JavaScript tool that allows you to listen for changes on JavaScript objects and arrays!

一直以来，关注对象属性的更改一直是人们追求的目标。 多年来，已经使用了许多垫片来监听对象的变化。 如今，我们有更好的方法来监听对象更改：Proxy API。 Sindre Sorhus创建了on-change ，这是一个微型JavaScript工具，可让您侦听JavaScript对象和数组上的变化！

不断变化JavaScript (on-change JavaScript)

Since the on-change code is so tiny, here it is in its full glory:

由于不断变化的代码是如此之小，因此这里充满了荣耀：

'use strict'; module.exports = (object, onChange) => { const handler = { get(target, property, receiver) { try { return new Proxy(target[property], handler); } catch (err) { return Reflect.get(target, property, receiver); } }, defineProperty(target, property, descriptor) { onChange(); return Reflect.defineProperty(target, property, descriptor); }, deleteProperty(target, property) { onChange(); return Reflect.deleteProperty(target, property); } }; return new Proxy(object, handler); };

The onChange function returns a proxy which you'll use to make any object changes.

onChange函数返回一个代理，您将使用该代理进行任何对象更改。

使用零钱 (Using on-change)

Pass onChange the object you'd like to spy on and a change handler function:

传递onChange您想要监视的对象和一个更改处理函数：

let j = { a: 1 }; // Upon change, save to server let changeable = onChange(j, () => save(j));

Then use that Proxy to change properties and get notified of changes:

然后使用该代理更改属性并获得更改通知：

// Make a change that would trigger changes changeable.a = 2; // save() is triggered! // j.a === 2

Note that the original object's values also change -- that's the beauty of Proxy!  Also note that on-change doesn't tell you which property changed; the use case, as Sindre describes, is saving an object (to server, etc.) when any part of an object changes.  You could also use ti for a small library with a render function, re-rendering the content whenever a property changed!

请注意，原始对象的值也会更改-这就是Proxy的美！ 还要注意，按变化并不能告诉您哪个属性已变化； 正如Sindre所描述的，用例是在对象的任何部分发生更改时将对象保存到服务器等。 您也可以将ti用于具有渲染功能的小型库，每当属性更改时就重新渲染内容！

This on-change library is really nice if you don't need to know which property changed, just that something changed.

这对改变图书馆是非常好的，如果你不需要知道哪个属性改变，只是事情发生了转变。

翻译自: https://davidwalsh.name/watch-object-changes

相关资源：jdk-8u281-windows-x64.exe