vue3中的數(shù)據(jù)劫持的最新實(shí)現(xiàn)方案的proxy示例詳解

更新時(shí)間：2024年11月25日 14:45:10 作者：風(fēng)清云淡_A

Vue3中使用Proxy實(shí)現(xiàn)數(shù)據(jù)劫持,解決了Vue2中數(shù)組和對(duì)象劫持的遺留問(wèn)題,Proxy可以修改某些操作的默認(rèn)行為,通過(guò)get和set方法實(shí)現(xiàn)數(shù)據(jù)的劫持和保護(hù)機(jī)制,感興趣的朋友跟隨小編一起看看吧

vuejs中實(shí)現(xiàn)數(shù)據(jù)的劫持,v2中使用的是Object.defineProperty()來(lái)實(shí)現(xiàn)的，在大版本v3中徹底重寫了這部分，使用了proxy這個(gè)數(shù)據(jù)代理的方式，來(lái)修復(fù)了v2中對(duì)數(shù)組和對(duì)象的劫持的遺留問(wèn)題。

proxy是什么

Proxy 用于修改某些操作的默認(rèn)行為，等同于在語(yǔ)言層面做出修改，所以屬于一種“元編程”（meta programming），即對(duì)編程語(yǔ)言進(jìn)行編程。
Proxy 可以理解成對(duì)源對(duì)象進(jìn)行一個(gè)封裝，在操作源對(duì)象之前，做了一系列額外的操作，最終返回我們需要的新數(shù)據(jù)對(duì)象。

基礎(chǔ)使用

let obj = new Proxy(
  {},
  {
    get(target, prop, receiver) {
      console.log("get", prop);
      if (!target[prop]) target[prop] = 120;
      return Reflect.get(target, prop, receiver);
    },
    set(target, prop, value, receiver) {
      console.log("set", prop);
      return Reflect.set(target, prop, value, receiver);
    },
  }
);
obj.count = 1;
obj.count;
obj.count;
obj.count;
console.log(obj.count);
obj.age;
console.log(obj.age);

proxy實(shí)例有兩個(gè)參數(shù)，一個(gè)是目標(biāo)對(duì)象，一個(gè)是操作方法的hash集合

取值函數(shù)get,賦值函數(shù)set。

對(duì)特定屬性的劫持

const proxyObj = new Proxy(
  { name: "Tom", age: 18 },
  {
    get: function (target, prop) {
      if (prop === "age") return target[prop] - 1;
      return 35;
    },
  }
);
proxyObj.time;
console.log("?? ~ proxyObj.time:", proxyObj.time);
proxyObj.age;
console.log("?? ~ proxyObj.time:", proxyObj.age);

把實(shí)例方法封裝在對(duì)象內(nèi)部

const object = {
  name: "Tom",
  age: 18,
  sayHi() {
    console.log("sayHi");
  },
  proxy() {
    return new Proxy(this, {
      get(target, prop) {
        console.log("?? ~ get ~ prop:", prop);
        if (prop in target) {
          return Reflect.get(target, prop);
        } else {
          return "no prop";
        }
        return Reflect.get(target, prop);
      },
    });
  },
};
const newProxy = object.proxy();
// newObjj.age;
console.log("?? ~ newObjj.age;:", newProxy.age);
console.log("?? ~ newObjj.name;:", newProxy.sex);

對(duì)數(shù)組進(jìn)行負(fù)值索引的操作

function createArray(...elements) {
  let handler = {
    get(target, prop, receiver) {
      let index = Number(prop);
      if (index < 0) {
        prop = String(target.length + index);
      }
      return Reflect.get(target, prop, receiver);
    },
  };
  let target = [];
  target.push(...elements);
  return new Proxy(target, handler);
}
let arr = createArray("a", "b", "c");
arr[-1];
console.log("?? ~ arr[-1]:", arr[-1]);
console.log("?? ~ arr[-1]:", arr[-2]);
console.log("?? ~ arr[-1]:", arr[-3]);

實(shí)現(xiàn)數(shù)據(jù)的鏈?zhǔn)秸{(diào)用

var double = (n) => n * 2;
var pow = (n) => Math.pow(n, 2);
var reverse = (n) => String(n).split("").reverse().join("");
const pipe = function (value) {
  var funcStack = [];
  var oProxy = new Proxy(
    {},
    {
      get: function (target, key) {
        console.log("?? ~ pipe ~ key:", key);
        if (key === "get") {
          return funcStack.reduce(function (val, func) {
            return func(val);
          }, value);
        }
        // 把方法存儲(chǔ)到棧中
        funcStack.push(window[key]);
        console.log("?? ~ funcStack:", funcStack);
        return oProxy;
      },
    }
  );
  return oProxy;
};
const data1 = pipe(3).double.pow.reverse.get;
console.log("?? ~ data:", data1);

注意：三個(gè)方法必須是var聲明的，let/const都會(huì)報(bào)錯(cuò)

上面代碼設(shè)置 Proxy 以后，達(dá)到了將函數(shù)名鏈?zhǔn)绞褂玫男Ч?/p>

利用get攔截，實(shí)現(xiàn)一個(gè)生成各種 DOM 節(jié)點(diǎn)的通用函數(shù)dom

const dom = new Proxy(
  {},
  {
    get(target, prop) {
      return function (arrts, ...children) {
        const el = document.createElement(prop);
        for (let prop of Object.keys(arrts)) {
          el.setAttribute(prop, arrts[prop]);
        }
        for (let child of children) {
          console.log("?? ~ get ~ child:", child);
          if (typeof child === "string") {
            child = document.createTextNode(child);
          }
          el.appendChild(child);
        }
        return el;
      };
    },
  }
);
const el = dom.div(
  {},
  "Hello, my name is ",
  dom.a({ href: "http://example.com" }, "Mark"),
  ". I like:",
  dom.ul(
    {},
    dom.li({}, "The web"),
    dom.li({}, "Food"),
    dom.li({}, "…actually that's it")
  )
);
document.body.appendChild(el);

第三個(gè)參數(shù)，它總是指向原始的讀操作所在的那個(gè)對(duì)象

const proxy = new Proxy(
  {},
  {
    get: function (target, prop, receiver) {
      console.log("?? ~ prop:", prop);
      return receiver;
    },
  }
);
const isSame = proxy.getReceiver === proxy;
console.log("?? ~ isSame:", isSame);
const d = Object.create(proxy);
console.log("ddd", d.a === d);

如果一個(gè)屬性不可配置（configurable）且不可寫（writable），則 Proxy 不能修改該屬性

const target = Object.defineProperties(
  {},
  {
    foo: { value: "bar", enumerable: false, configurable: false },
  }
);
const handler = {
  get(target, prop) {
    return "abc";
  },
};
const proxy2 = new Proxy(target, handler);
proxy2.foo;

上面通過(guò) Proxy 對(duì)象訪問(wèn)該屬性會(huì)報(bào)錯(cuò)。

攔截方法的執(zhí)行

上面的都是object對(duì)象的屬性進(jìn)行劫持，也可以作為方法調(diào)用時(shí)進(jìn)行劫持。

var target = function () {
  return "I am the target";
};
var handler = {
  apply(target, thisArg, argumentsList) {
    console.log("?? ~ apply ~ argumentsList:", argumentsList);
    const res = target();
    console.log("?? ~ apply ~ res:", res);
    return "I am the proxy" + " " + argumentsList.join(",");
  },
};
const p = new Proxy(target, handler);
const a = p("a", "b");
console.log("?? ~ a:", a);

變量p是 Proxy 的實(shí)例，當(dāng)它作為函數(shù)調(diào)用時(shí)（p()），就會(huì)被apply方法攔截，返回一個(gè)字符串

function sum(left, right) {
  return left + right;
}
var twice = {
  apply(target, context, args) {
    console.log("?? ~ apply ~ context:", context);
    console.log("?? ~ apply ~ args:", args);
    return Reflect.apply(target, context, args) * 2;
  },
};
const proxy = new Proxy(sum, twice);
const data = proxy(1, 2);
console.log("?? ~ data:", data);
const data2 = proxy.call(null, 2, 5);
console.log("?? ~ data2:", data2);
const data3 = proxy.apply(null, [5, 5]);
console.log("?? ~ data3:", data3);

當(dāng)執(zhí)行proxy函數(shù)（直接調(diào)用或call和apply調(diào)用），就會(huì)被apply方法攔截。

get和set方法，實(shí)現(xiàn)內(nèi)部屬性的保護(hù)機(jī)制

const proxy = new Proxy(
  {},
  {
    get(target, prop) {
      invariant(prop, "get");
      return Reflect.get(target, prop);
    },
    set(target, prop, value) {
      invariant(prop, "set");
      Reflect.set(target, prop, value);
      return true;
    },
  }
);
function invariant(key, action) {
  if (key[0] === "_") {
    throw new Error(`Invalid attempt to ${action} private "${key}" property`);
  }
}
// proxy._prop;
proxy._prop = "value";

攔截key in proxy的操作

var target = { _prop: "foo", prop: "foo" };
const proxy = new Proxy(target, {
  has(target, key) {
    if (key[0] === "_") {
      console.log("false");
      return false;
    }
    return key in target;
  },
});
"_prop" in proxy; // false

deleteProperty刪除屬性的劫持

const handler = {
  construct(target, args) {
    console.log("called: " + args.join(","));
    return new target(...args);
  },
  deleteProperty(target, prop) {
    if (prop === "age") return false;
    delete target[prop];
    return true;
  },
};
const P = new Proxy(function () {}, handler);
const p = new P(10);
P.value;
const p2 = new Proxy(
  {
    age: 20,
    name: "John",
    greet: () => console.log("hello"),
  },
  handler
);
delete p2.age;
delete p2.name;