In ES6 done some expansion and optimization methods for the object, the following brief summary under the common method
The method of determining whether two objects is congruent
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console.log(Object.is({},{}), {} === {});
// false, false
console.log(Object.is(NaN,NaN), NaN === NaN);
// true, false
console.log(Object.is(+0,-0), +0 === -0);
// false, true
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A method for copy assign object properties
If the two parameters, the second parameter may be enumerated attributes to the first copy of the argument object is limited to be enumerated property, if there is a plurality of parameters, then copying the same
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var
obj = {};
var
obj2 = Object.assign(obj,{name:
'Joh'
},{age:10});
console.log(obj === obj2, obj);
// true, {name:'Joh', age:10}
console.log(Object.is(obj,obj2));
// true
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Copies of the same covering properties
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const DEFAULT_OPTIONS = {
name:
"Joh"
};
function
test(opts) {
let options = Object.assign({}, DEFAULT_OPTIONS, opts);
console.log(options);
}
test();
// {name: "Joh"}
test({name:
"Lily"
,age:10});
// {name: "Lily", age: 10}
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Symbol attribute the same copy
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var
skey1 = Symbol(
'test'
);
var
skey2 = Symbol(
'test'
);
var
obj = {};
Object.assign(obj,{name:
'Joh'
},{age:10},{[skey1]:
'I am test1'
},{[skey2]:
'I am test2'
});
// 拷贝
// 验证Symbol的拷贝成功
console.log(obj[skey1]);
// I am test
console.log(obj);
// {name: "Joh", age: 10, Symbol(test): "I am test1", Symbol(test): "I am test2"}
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Object方法：keys，getOwnPropertyNames， getOwnPropertySymbols，getOwnPropertyDescriptor的应用
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class A {
constructor() {
this
.name =
'Joh'
;
}
[Symbol(
'fullnameA'
)] () {
}
getName() {
}
}
class B extends A {
constructor() {
super
();
this
.age = 22;
}
[Symbol(
'fullnameB'
)] () {
}
getAge() {
}
}
B.prototype.getColor =
function
() {};
var
b =
new
B();
// 备注：只能获取【自身可枚举属性】，但得不到【原型链上的属性(比如方法) + Symbols属性】
console.log(Object.keys(b));
// ["name", "age"]
// 备注：可获取【可枚举属性】,但得不到【原型链上的属性 + Symbols属性】
console.log(Object.getOwnPropertyNames(b));
// ["name", "age"]
// 使用keys怎么也得不到原型链上不可枚举的属性[通过语法糖创建的方法]
console.log(Object.keys(B.prototype));
// ["getColor"]
// 使用 getOwnPropertyNames 传入prototype 可以得到原型链上的属性
console.log(Object.getOwnPropertyNames(B.prototype));
// ["constructor", "getColor", "getAge"]
// 通过getOwnPropertySymbols可以得到自身Symbols属性，但得不到继承的Symbol属性
console.log(Object.getOwnPropertySymbols(B.prototype));
// [Symbol(fullnameB)]
// 获取自身可枚举属性包括继承过来的，备注：通过class内部的语法糖创建的方法是不可枚举的，但是通过后期B.prototype.出来的是可枚举的
for
(let key
in
b) {
console.log(key);
// 依次输出 name 和 age 和 getColor
}
// 描述对象 测试可枚举性
console.log(Object.getOwnPropertyDescriptor(B.prototype,
'getColor'
));
console.log(Object.getOwnPropertyDescriptor(B.prototype,
'getColor'
).enumerable);
// true
console.log(Object.getOwnPropertyDescriptor(B.prototype,
'getAge'
).enumerable);
// false
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