在上一篇文章里介绍了使用 jQuery 的事件来实现数据视图双向绑定，并且提到 Object.defineProperty。这篇文章专门详解如何用 Object.defineProperty 方法同样实现数据视图双向绑定的功能。
Object.defineProperty 是用来控制 Javascript 对象属性读取行为的方法，用法很直白：
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Object.defineProperty(obj, 'key', { get: () => { console.log('obj->key is got and always return 1'); return 1; }, set: (val) => { console.log('obj->key is set and nothing happend'); } }); |
其中第二个参数是对象的属性名，第三个参数是行为的配置。除了可以对属性值获取以及复制行为进行控制以外，还可以配置是否可写，是否可被遍历等，具体的配置参数在 MDN 相关章节解释得很清楚，我这就不多说了，这里我能用上的也只有 get 和 set 而已。
利用 Object.defineProperty 做双向绑定的具体思路：
- 利用 get，将页面上的某个地方显示的数据，绑定到对象上
123Object.defineProperty(product, 'price', {get: () => +document.getElementById('某个 price 的 id').innerText}); - 利用 set，当对象的属性发生改变时，更新到视图上
12345Object.defineProperty(product, 'num', {set: (num) => {document.getElementById('某个商品数量的 id').innerHTML = num;}});
完整的代码示例：
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<!DOCTYPE html> <html lang="zh-CN"> <head> <meta charset="utf-8"> <meta http-equiv="X-UA-Compatible" content="IE=edge"> <meta name="viewport" content="width=device-width, initial-scale=1"> <title>Demo</title> </head> <body> <ul id="cart"> <li class="product"> 单价 $<span class="price">1</span> <button class="incre">+</button> <input type="number" class="number" value="1"> <button class="decre" disabled>-</button> 单品总价：$<span class="total-price">1</span> </li> <li class="product"> 单价 $<span class="price">3</span> <button class="incre">+</button> <input type="number" class="number" value="2"> <button class="decre">-</button> 单品总价：$<span class="total-price">6</span> </li> </ul> <p>总数量：<span id="total-num">3</span></p> <p>总价：$<span id="total-price">7</span></p> <script> // 定义购物车数据模型 var cart = { setProducts: (products) => { cart.products = products; cart.check(); }, check: () => { var num = 0; var price = 0; cart.products.forEach((product) => { num += product.num; price += product.getTotalPrice(); }); cart.num = num; cart.price = price; }, }; class Product { getTotalPrice() { return this.num * this.price; } setNum(num) { this.num = Math.min(Math.max(num, 1), 10); cart.check(); } canIncre() { return this.num < 10; // 假设库存都为 10 } canDecre() { return this.num > 1; } incre() { this.setNum(this.num + 1); } decre() { this.setNum(this.num - 1); } } (() => { var $products = document.querySelectorAll('.product'); var products = []; for (var i = 0; i < $products.length; ++i) { let $product = $products[i]; let product = new Product(); Object.defineProperty(product, 'price', { value: +$product.querySelector('.price').innerText }); Object.defineProperty(product, 'num', { get: () => +$product.querySelector('.number').value, set: (num) => { $product.querySelector('.number').value = num; $product.querySelector('.total-price').innerHTML = product.getTotalPrice(); $product.querySelector('.incre').disabled = !product.canIncre(); $product.querySelector('.decre').disabled = !product.canDecre(); } }); $product.querySelector('.incre').addEventListener('click', () => { product.incre(); }); $product.querySelector('.decre').addEventListener('click', () => { product.decre(); }); $product.querySelector('.number').addEventListener('change', (e) => { product.setNum(e.target.value); }); products.push(product); } Object.defineProperty(cart, 'num', { set: (num) => { document.getElementById('total-num').innerHTML = num; } }); Object.defineProperty(cart, 'price', { set: (price) => { document.getElementById('total-price').innerHTML = price; } }); cart.setProducts(products); })(); </script> </body> </html> |
数据视图双向绑定（纯 JS 利用 Object.defineProperty 实现） by Chrisyue's Blog is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.