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  • 使用defineProperty进行双向绑定的原理

    <!DOCTYPE html>
    <html>
    
    <head>
        <title>defineProperty</title>
    </head>
    
    <body>
        name:<input type="text" id="name">
        age:<input type="number" id="age">
        <br />
        <br />
        name:<span id="namep"></span>
        <br />
        age:<span id="agep"></span>
    
        <script type="text/javascript">
        function Obj() {
    
        }
        Obj.prototype.data = {
            name: "mvvm",
            age: 18
        }
    
        let dataObj = new Obj();
    
        Object.keys(dataObj.data).forEach(key => {
            Object.defineProperty(dataObj, key, {
                get: function() {
                    return dataObj[key];
                },
                set: function(newValue) {
                    document.getElementById(`${key}p`).innerHTML = newValue;
                    dataObj.data[key] = newValue;
                }
            });
        });
    
        document.getElementById("name").addEventListener('keyup', function(e) {
            dataObj["name"] = e.target.value;
        });
    
        document.getElementById("age").addEventListener('keyup', function(e) {
            dataObj["age"] = e.target.value;
        });
        </script>
    </body>
    
    </html>
    <!DOCTYPE html>
    <html>
    
    <head>
        <title>KOA</title>
    </head>
    
    <body>
        <input type="text" k-value="value" id="input" />
        <div k-text="value" id="el"></div>
        <script type="text/javascript">
        /**基本思路是使用Object.defineProperty对数据对象做属性get和set的监听,当有数据读取和赋值操作时则调用节点的指令,这样使用最通用的=等号赋值就可以了。*/
        var elems = [document.getElementById('el'), document.getElementById('input')];
        var data = {
            value: "hello"
        };
    
        var command = {
            text: function(str) {
                this.innerHTML = str;
            },
            value: function(str) {
                this.setAttribute('value', str);
            }
        }
    
        let scan = function() {
            for (let i = 0, len = elems.length; i < len; i++) {
                let elem = elems[i];
                elem.command = [];
                for (let j = 0, len1 = elem.attributes.length; j < len1; j++) {
                    let attr = elem.attributes[j];
                    if (attr.nodeName.indexOf('k-') >= 0) {
                        //调用属性指令
                        command[attr.nodeName.slice(2)].call(elem, data[attr.nodeValue]);
                        elem.command.push(attr.nodeName.slice(2));
                    }
                }
            }
        }
    
        let bValue;
    
        /**
         * 定义属性劫持
         */
        let defineGetAndSet = function(obj, propName) {
            try {
                Object.defineProperty(obj, propName, {
                    get: function() {
                        return bValue;
                    },
                    set: function(newValue) {
                        bValue = newValue;
                        scan();
                    },
                    enumerable: true,
                    configurable: true
                });
            } catch (err) {
                console.log("browser not supported");
            }
        }
    
        //初始化数据
        scan();
    
        defineGetAndSet(data, 'value');
    
        if (document.addEventListener) {
            elems[1].addEventListener('keyup', function(e) {
                data.value = e.target.value;
            }, false);
        } else {
            elems[1].attachEvent('onkeyup', function(e) {
                data.value = e.target.value;
            }, false);
        }
    
        setTimeout(function(){
            data.value = 'hello kruce';
        }, 2000)
        </script>
    </body>
    
    </html>
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  • 原文地址:https://www.cnblogs.com/KruceCoder/p/10554062.html
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