vue3의 반응성()에 대해 자세히 이야기해 봅시다.

<script setup>
import {reactive} from &#39;vue&#39;
const data = reactive({ //定义对象
  name:&#39;测试&#39;,
  age:10
})
const num = reactive(1)//定义基本数据类型
console.log(data)//便于定位到调试位置
</script>
<template>
<div>
<h1 id="nbsp-data-name-nbsp">{{ data.name }}</h1>
</div>
</template>

<style scoped></style>

/*1.初始进来函数，判断目标对象target是否为只读对象，如果是直接返回*/
function reactive(target) {
    // if trying to observe a readonly proxy, return the readonly version.
    if (isReadonly(target)) {
        return target;
    }
    //创建一个reactive对象，五个参数后续会讲解
    return createReactiveObject(target, false, mutableHandlers, mutableCollectionHandlers, reactiveMap);
}


/*2.判断是来判断target是否为只读。*/
function isReadonly(value) {
    return !!(value && value["__v_isReadonly" /* ReactiveFlags.IS_READONLY */]);
}

/*3.创建一个reactive对象*/
/*createReactiveObject接收五个参数：
target被代理的对象，
isReadonl是不是只读的，
baseHandlers proxy的捕获器，
collectionHandlers针对集合的proxy捕获器，
proxyMap一个用于缓存proxy的`WeakMap`对象*/
function createReactiveObject(target, isReadonly, baseHandlers, collectionHandlers, proxyMap) {
//如果target不是对象则提示并返回
/*这里会跳转到如下方法
判断是否原始值是否为object类型 
const isObject = (val) => val !== null && typeof val === 'object';
*/
    if (!isObject(target)) {
        if ((process.env.NODE_ENV !== 'production')) {
            console.warn(`value cannot be made reactive: ${String(target)}`);
        }
        return target;
    }
    // 如果target已经是proxy是代理对象则直接返回.
    if (target["__v_raw" /* ReactiveFlags.RAW */] &&
        !(isReadonly && target["__v_isReactive" /* ReactiveFlags.IS_REACTIVE */])) {
        return target;
    }
    // 从proxyMap中获取缓存的proxy对象，如果存在的话，直接返回proxyMap中对应的proxy。否则创建proxy。
    const existingProxy = proxyMap.get(target);
    if (existingProxy) {
        return existingProxy;
    }
    // 并不是任何对象都可以被proxy所代理。这里会通过getTargetType方法来进行判断。
    const targetType = getTargetType(target);
    //当类型值判断出是不能代理的类型则直接返回
    if (targetType === 0 /* TargetType.INVALID */) {
        return target;
    }
    //通过使用Proxy函数劫持target对象，返回的结果即为响应式对象了。这里的处理函数会根据target对象不同而不同(这两个函数都是参数传入的)：
    //Object或者Array的处理函数是collectionHandlers;
    //Map,Set,WeakMap,WeakSet的处理函数是baseHandlers;
    const proxy = new Proxy(target, targetType === 2 /* TargetType.COLLECTION */ ? collectionHandlers : baseHandlers);
    proxyMap.set(target, proxy);
    return proxy;
}

//1.进入判断如果value有__v_skip属性且为true或对象是可拓展则返回0，否则走类型判断函数
function getTargetType(value) {
//Object.isExtensible() 方法判断一个对象是否是可扩展的（是否可以在它上面添加新的属性）。
    return value["__v_skip" /* ReactiveFlags.SKIP */] || !Object.isExtensible(value)
        ? 0 /* TargetType.INVALID */
        : targetTypeMap(toRawType(value));
}
//2.这里通过Object.prototype.toString.call(obj)来判断数据类型
const toRawType = (value) => {
    // extract "RawType" from strings like "[object RawType]"
    return toTypeString(value).slice(8, -1);
};
const toTypeString = (value) => objectToString.call(value);
//3.这里rawType是为'Object'所以会返回1
function targetTypeMap(rawType) {
    switch (rawType) {
        case 'Object':
        case 'Array':
            return 1 /* TargetType.COMMON */;
        case 'Map':
        case 'Set':
        case 'WeakMap':
        case 'WeakSet':
            return 2 /* TargetType.COLLECTION */;
        default:
            return 0 /* TargetType.INVALID */;//返回0说明除前面的类型外其他都不能被代理，如Date，RegExp，Promise等
    }
}

const mutableHandlers = {
    get,// 获取值的拦截，访问对象时会触发
    set,// 更新值的拦截，设置对象属性会触发
    deleteProperty,// 删除拦截，删除对象属性会触发
    has,// 绑定访问对象时会拦截，in操作符会触发
    ownKeys// 获取属性key列表
};

function deleteProperty(target, key) {
    // key是否是target自身的属性
    const hadKey = hasOwn(target, key);
    // 旧值
    const oldValue = target[key];
    // 调用Reflect.deleteProperty从target上删除属性
    const result = Reflect.deleteProperty(target, key);
    // 如果删除成功并且target自身有key，则触发依赖
    if (result && hadKey) {
        trigger(target, "delete" /* TriggerOpTypes.DELETE */, key, undefined, oldValue);
    }
    return result;
}
//
function has(target, key) {
    //检查目标对象是否存在此属性。
    const result = Reflect.has(target, key);
    // key不是symbol类型或不是symbol的内置属性，进行依赖收集
    if (!isSymbol(key) || !builtInSymbols.has(key)) {
        track(target, "has" /* TrackOpTypes.HAS */, key);
    }
    return result;
}
/*ownKeys可以拦截以下操作:
1.Object.keys()
2.Object.getOwnPropertyNames()
3.Object.getOwnPropertySymbols()
4.Reflect.ownKeys()操作*/
function ownKeys(target) {
    track(target, "iterate" /* TrackOpTypes.ITERATE */, isArray(target) ? 'length' : ITERATE_KEY);
    return Reflect.ownKeys(target);
}

const get = /*#__PURE__*/ createGetter();
/*传递两个参数默认都为false
isReadonly是否为只读
shallow是否转换为浅层响应，即Reactive---> shallowReactive，shallowReactive监听了第一层属性的值，一旦发生改变，则更新视图;其他层，虽然值发生了改变，但是视图不会进行更新
*/
function createGetter(isReadonly = false, shallow = false) {
    return function get(target, key, receiver) {
    //1.是否已被reactive相关api处理过；
        if (key === "__v_isReactive" /* ReactiveFlags.IS_REACTIVE */) {
            return !isReadonly;
        }
     //2.是否被readonly相关api处理过
        else if (key === "__v_isReadonly" /* ReactiveFlags.IS_READONLY */) {
            return isReadonly;
        }
        else if (key === "__v_isShallow" /* ReactiveFlags.IS_SHALLOW */) {
            return shallow;
        }
      //3.检测__v_raw属性
        else if (key === "__v_raw" /* ReactiveFlags.RAW */ &&
            receiver ===
                (isReadonly
                    ? shallow
                        ? shallowReadonlyMap
                        : readonlyMap
                    : shallow
                        ? shallowReactiveMap
                        : reactiveMap).get(target)) {
            return target;
        }
      //4.如果target是数组，且命中了一些属性，则执行函数方法
        const targetIsArray = isArray(target);
        if (!isReadonly && targetIsArray && hasOwn(arrayInstrumentations, key)) {
            return Reflect.get(arrayInstrumentations, key, receiver);
        }
      //5.Reflect获取值
        const res = Reflect.get(target, key, receiver);
      //6.判断是否为特殊的属性值
        if (isSymbol(key) ? builtInSymbols.has(key) : isNonTrackableKeys(key)) {
            return res;
        }
        if (!isReadonly) {
            track(target, "get" /* TrackOpTypes.GET */, key);
        }
        if (shallow) {
            return res;
        }
      //7.判断是否为ref对象
        if (isRef(res)) {
            // ref unwrapping - skip unwrap for Array + integer key.
            return targetIsArray && isIntegerKey(key) ? res : res.value;
        }
      //8.判断是否为对象
        if (isObject(res)) {
            // Convert returned value into a proxy as well. we do the isObject check
            // here to avoid invalid value warning. Also need to lazy access readonly
            // and reactive here to avoid circular dependency.
            return isReadonly ? readonly(res) : reactive(res);
        }
        return res;
    };
}

const set = /*#__PURE__*/ createSetter();
  //shallow是否转换为浅层响应，默认为false
function createSetter(shallow = false) {
    //1.传递四个参数
    return function set(target, key, value, receiver) {
        let oldValue = target[key];
        //首先获取旧值，如果旧值是ref类型，且新值不是ref类型，则不允许修改
        if (isReadonly(oldValue) && isRef(oldValue) && !isRef(value)) {
            return false;
        }
     //2.根据传递的shallow参数，来执行之后的操作
        if (!shallow) {
            if (!isShallow(value) && !isReadonly(value)) {
                oldValue = toRaw(oldValue);
                value = toRaw(value);
            }
            if (!isArray(target) && isRef(oldValue) && !isRef(value)) {
                oldValue.value = value;
                return true;
            }
        }
      //3.检测key是不是target本身的属性
        const hadKey = isArray(target) && isIntegerKey(key)
            ? Number(key) < target.length
            : hasOwn(target, key);
        //利用Reflect.set()来修改值,返回一个Boolean值表明是否成功设置属性
        //Reflect.set(设置属性的目标对象, 设置的属性的名称, 设置的值, 如果遇到 `setter`，`receiver`则为`setter`调用时的`this`值)
        const result = Reflect.set(target, key, value, receiver);
        // 如果目标是原始原型链中的某个元素，则不要触发
        if (target === toRaw(receiver)) {
        //如果不是target本身的属性那么说明执行的是&#39;add&#39;操作,增加属性
            if (!hadKey) {
                trigger(target, "add" /* TriggerOpTypes.ADD */, key, value);
            }
      //4.比较新旧值，是否触发依赖
            else if (hasChanged(value, oldValue)) {
      //5.触发依赖
                trigger(target, "set" /* TriggerOpTypes.SET */, key, value, oldValue);
            }
        }
        return result;
    };
}

    if (target["__v_raw" /* ReactiveFlags.RAW */] &&
        !(isReadonly && target["__v_isReactive" /* ReactiveFlags.IS_REACTIVE */])) {
                return target;
    }

<script setup>
import { reactive,ref } from "vue";
const data = reactive({
  name: "测试",
  age: 10,
});
const numRef = ref(1)
const dataRef = ref({
  name: "测试2",
  age: 20,
})
const num = reactive(numRef)
const dataReactive = reactive(dataRef)
console.log(&#39;data&#39;,data)
console.log(&#39;numRef&#39;,numRef)
console.log(&#39;num&#39;,num)
console.log(&#39;dataRef&#39;,dataRef)
console.log(&#39;dataReactive&#39;,dataReactive)
</script>

<script setup>
import { reactive } from "vue";
const mapData = new Map();
mapData.set(&#39;name&#39;,&#39;张三&#39;)
const setData = new Set([1,2,3,1,1])
console.log(mapData)
console.log(setData)
const mapReactive = reactive(mapData)
console.log(mapReactive)
</script>

const targetType = getTargetType(target);

function getTargetType(value) {
    return value["__v_skip" /* ReactiveFlags.SKIP */] || !Object.isExtensible(value)
        ? 0 /* TargetType.INVALID */
        : targetTypeMap(toRawType(value));
}

function targetTypeMap(rawType) {//rawType="Map",这里返回值为2
    switch (rawType) {
        case 'Object':
        case 'Array':
            return 1 /* TargetType.COMMON */;
        case 'Map':
        case 'Set':
        case 'WeakMap':
        case 'WeakSet':
            return 2 /* TargetType.COLLECTION */;
        default:
            return 0 /* TargetType.INVALID */;
    }
}

const mutableCollectionHandlers = {
    get: /*#__PURE__*/ createInstrumentationGetter(false, false)
};

//解构createInstrumentations
const [mutableInstrumentations, readonlyInstrumentations, shallowInstrumentations, shallowReadonlyInstrumentations] = /* #__PURE__*/ createInstrumentations();
//传入两个参数，是否为可读，是否为浅层响应
function createInstrumentationGetter(isReadonly, shallow) {
    const instrumentations = shallow
        ? isReadonly
            ? shallowReadonlyInstrumentations
            : shallowInstrumentations
        : isReadonly
            ? readonlyInstrumentations
            : mutableInstrumentations;
    return (target, key, receiver) => {
        if (key === "__v_isReactive" /* ReactiveFlags.IS_REACTIVE */) {
            return !isReadonly;
        }
        else if (key === "__v_isReadonly" /* ReactiveFlags.IS_READONLY */) {
            return isReadonly;
        }
        else if (key === "__v_raw" /* ReactiveFlags.RAW */) {
            return target;
        }
        return Reflect.get(hasOwn(instrumentations, key) && key in target
            ? instrumentations
            : target, key, receiver);
    };
}

//篇幅问题以及这方面笔者并未深入，所以就大概带过
function createInstrumentations() {
//创建了四个对象，对象内部有很多方法,其他去掉了，完整可自行去调试查看
    const mutableInstrumentations = {
        get(key) {
            return get$1(this, key);
        },
        get size() {
            return size(this);
        },
        has: has$1,
        add,
        set: set$1,
        delete: deleteEntry,
        clear,
        forEach: createForEach(false, false)
    };
    
    .................
    
    //通过createIterableMethod方法操作keys、values、entries、Symbol.iterator迭代器方法
    const iteratorMethods = ['keys', 'values', 'entries', Symbol.iterator];
    iteratorMethods.forEach(method => {
        mutableInstrumentations[method] = createIterableMethod(method, false, false);
        readonlyInstrumentations[method] = createIterableMethod(method, true, false);
        shallowInstrumentations[method] = createIterableMethod(method, false, true);
        shallowReadonlyInstrumentations[method] = createIterableMethod(method, true, true);
    });
    return [
        mutableInstrumentations,
        readonlyInstrumentations,
        shallowInstrumentations,
        shallowReadonlyInstrumentations
    ];
}