一、hasOwnProperty vs isPrototyOf
1&2互为补充
function siteAdmin(nickName,siteName){
this.nickName=nickName;
this.siteName=siteName;
}
siteAdmin.prototype.showAdmin = function() {
alert(this.nickName+"是"+this.siteName+"的站长!")
};
siteAdmin.prototype.showSite = function(siteUrl) {
this.siteUrl=siteUrl;
return this.siteName+"的地址是"+this.siteUrl;
};
var matou=new siteAdmin("脚本之家","WEB前端开发");
var matou2=new siteAdmin("脚本之家","WEB前端开发");
1. hasOwnProperty: 对象求属性，但是不包括原型链里的。
alert(matou.hasOwnProperty("nickName"));//true
alert(matou.hasOwnProperty("age"));//true
alert(matou.hasOwnProperty("showAdmin"));//false
alert(matou.hasOwnProperty("siteUrl"));//false
alert(siteAdmin.prototype.hasOwnProperty("showAdmin"));//true
alert(siteAdmin.prototype.hasOwnProperty("siteUrl"));//false
2. isPropertyof对象是否继承与某个原型链。 判断某个原型链，该对象有没有继承。
alert(siteAdmin.prototype.isPrototypeOf(matou))//true
二、object.create (shadowcopy and 原型链继承) / object freeze
const obj = {
data: 1,
compositor: {
b: 2,
c: {
data: 2,
},
},
m: undefined,
get: () => {
return this.xxx.data;
},
};
const test1 = obj;
test1.data = 2;
console.log(obj); // { data: 1, compositor: { b: 2 }, get: [Function: get] }
console.log(JSON.parse(JSON.stringify(obj))); //!missing get { data: 1, compositor: { b: 2 } }
const test3 = { ...obj };
test3.compositor.b = 4;
console.log(obj);
console.log(test3);
const test = Object.create(obj); //!test的原型链继承了obj shalowcopy the property
test.__proto__.data = 3;
test.__proto__.compositor.b = 3;
console.log(test.__proto__); //!should be __proto__
//!test shadow
const objclone = {
compositor: {
data: {
m: 3,
},
},
get: () => {
return this.xxx.m;
},
};
const test33 = { ...objclone };
test33.compositor.data = 4;
console.log(objclone);
console.log(test33);
//! deepcopy success
const test34 = { ...objclone };
test34.compositor = { data: 6 };
console.log(objclone);
console.log(test34);
function deepcopy(obj1) {
if (typeof obj1 != "object" || obj1 == null) return obj1;
var newObj = obj1.constructor();
console.log(newObj);
for (let prop in obj1) {
if (typeof obj1[prop] == "object") {
newObj[prop] = deepcopy(obj1[prop]);
} else {
newObj[prop] = obj1[prop];
}
}
return newObj;
}
function typeString(obj) {
var cons = Object.prototype.toString.call(obj).slice(8, -1);
return cons === "Array" || cons === "Object";
}
const testfinal = deepcopy(obj);
testfinal.compositor.c.data = 6;
console.log("deepcopy", deepcopy(obj));
console.log("deepcopy", deepcopy(testfinal));
三、object.freeze
freeze是对object的属性操作， 增删改都不会骑作用， 但是不会报错， 只有在'strict'模式下才会throw error
freeze也是浅冷冻， 如果真的想所有的起效， 需要deepFreeze, 也就是递归
freeze是堆内存，不是栈内存，所以可以赋值改变
function deepFreeze(obj) {
if (typeof obj != "object" || obj === null) return obj;
for (let prop in obj) {
if (typeof obj[prop] == "object" && obj != null) {
obj[prop] = deepFreeze(obj[prop]);
}
}
return Object.freeze(obj);
}
deepFreeze(obj);
obj.b.c = 13; //不会报错
console.log(obj); //仍然是 {"a":5}