关于vue2响应式缺陷的问题

// 直接通过下标来修改，没有响应式
fn1() {
    this.arr[0] = 100
}

//修改数组的length
fn2 () {
    this.arr.length = 0
}

fn1 () {
    // 方法1： 先删除，再添加
    this.arr.splice(0,1,100)
},
fn2 () {
    // 方法2： $set
    this.$set(this.arr, "0", 100)
}

const { arrayMethods } = require('./array')
 
class Observer {
    constructor(value) {
        Object.defineProperty(value, '__ob__', {
            value: this,
            enumerable: false,
            writable: true,
            configurable: true
        })
        if(Array.isArray(value)) {
            value.__proto__ = arrayMethods
            this.observeArray(value)
        } else {
            this.walk(value)
        }
    }
 
    walk(data) {
        let keys = Object.keys(data)
        for(let i = 0; i < keys.length; i++) {
            const key = keys[i]
            const value = data[key]
            defineReactive(data, key, value)
        }
    }
 
    observeArray(items) {
        for(let i = 0; i < items.length; i++) {
            observe(items[i])
        }
    }
}
 
function defineReactive(data, key, value) {
    const childOb = observe(value)
 
    const dep = new Dep()
 
    Object.defineProperty(data, key, {
        get() {
            console.log('获取值')
            if (Dep.target) {
                dep.depend()
 
                if (childOb) {
                    childOb.dep.depend()
 
                    if (Array.isArray(value)) {
                        dependArray(value)
                    }
                }
            }
            return value
        },
        set(newVal) {
            if (newVal === value) return
            observe(newVal)
            value = newVal
            dep.notify()
        }
    })
}
 
function observe(value) {
    if (Object.prototype.toString.call(value) === '[object Object]' || Array.isArray(value)) {
        return new Observer(value)
    }
}
 
function dependArray(value) {
    for(let e, i = 0, l = value.length; i < l; i++) {
        e = value[i]
 
        e && e.__ob__ && e.__ob__.dep.depend()
 
        if (Array.isArray(e)) {
            dependArray(e)
        }
    }
}
 
// array.js
const arrayProto = Array.prototype
 
const arrayMethods = Object.create(arrayProto)
 
const methodsToPatch = [
    'push',
    'pop',
    'shift',
    'unshift',
    'splice',
    'reverse',
    'sort'
]
 
methodsToPatch.forEach(method => {
    arrayMethods[method] = function (...args) {
        const result = arrayProto[method].apply(this, args)
 
        const ob = this.__ob__
 
        var inserted
 
        switch (method) {
            case 'push':
            case 'unshift':
                inserted = args
                break;
            case 'splice':
                inserted = args.slice(2)
            default:
                break;
        }
 
        if (inserted) ob.observeArray(inserted)
 
        ob.dep.notify()
 
        return result
    }
})
 

        let person = {
            name: '张三',
            age: 18
        }
        const p = new Proxy(person, {
            get(target, propName) {
                console.log(`我的${propName}值被获取了`);
                return Reflect.get(target, propName)
            },
            set(target, propName, value) {
                console.log(`我的${propName}值被修改了`);
                Reflect.set(target, propName, value)
            },
            deleteProperty(target, propName) {
                console.log(`我的${propName}值被删除了`);
                Reflect.deleteProperty(target, propName)
            }
        })