企业宣传画册制作报价/福州百度首页优化

1、Object.entries()

Object.entries() 可以把一个对象的键值以数组的形式遍历出来，结果和for...in...一样，但是不会遍历原型属性

例子a: ---传入对象 

const obj = { foo: 'bar', baz: 'abc' }; 
console.log(Object.entries(obj));  // [['foo', 'bar'], ['baz', 'abc']]

例子b: ---传入数组

const arr = [1, 2, 3]; 
console.log(Object.entries(arr));  // [['0', 1], ['1', '2'], ['2', '3']]

例子c: ---传入包含对象的数组

const arr1 = [{ a: 1 }, 2, 3]; 
console.log(Object.entries(arr1));  // [['0', { a: 1 }], ['1', '2'], ['2', '3']]

例子d: ---传入全部是对象的数组

const arr2 = [{ a: 1 }, { b: 2 }, { c: 3 }]; 
console.log(Object.entries(arr2));  // [['0', { a: 1 }], ['1', { b: 2 }], ['2', { c: 3 }]]

例子e: ---传入字符串

const str = '123'; 
console.log(Object.entries(str));  // [['0', '1'], ['1', '2'], ['2', '3']]

例子f: ---传入数字、浮点数

const num = 123; 
console.log(Object.entries(num));  // []

const float1 = 12.3; 
console.log(Object.entries(float1));  // []

例子g: ---将Object转化为Map

const obj2 = { foo: 'bar', baz: 'abc' }; 
console.log(Object.entries(obj2));  // [['foo', 'bar'], ['baz', 'abc']]
const map = new Map(Object.entries(obj2)); 
console.log(map); // Map {'foo' => 'bar', 'baz' => 'abc'}

2、Object.assign(target,source1,source2,...)

此方法只拷贝源对象的自身属性，不拷贝继承的属性。

Object.assign方法实行的是浅拷贝，而不是深拷贝。也就是说，如果源对象某个属性的值是对象，那么目标对象拷贝得到的是这个对象的引用。同名属性会替换。
Object.assign只能进行值的复制，如果要复制的值是一个取值函数，那么将求值后再复制。
Object.assign可以用来处理数组，但是会把数组视为对象。 

const target = { x : 0,y : 1};
const source = { x : 1,z : 2 ,fn : {number : 1}};
console.log(Object.assign(target, source));
// target  {x : 1, y : 1, z : 2, fn : {number : 1}}    // 同名属性会被覆盖
target.fn.number = 2;
console.log(source)// source  {x : 1, z : 2, fn : {number : 2}}   // 拷贝为对象引用

function Person(){this.name = 1
};
Person.prototype.country = 'china';
var student = new Person();
student.age = 29 ;
const young = {name : 'zhang'};
Object.assign(young,student);
// young {name : 'zhang', age : 29}               // 只能拷贝自身的属性，不能拷贝prototype

Object.assign([1, 2, 3], [4, 5])                      // 把数组当作对象来处理
// [4, 5, 3]// {0:1, 1:2, 2:3} {0:4, 1:5}

例子a: 合并对象

var first = { name: "Bob" };
var last = { lastName: "Smith" };var person = Object.assign(first, last);
console.log(person);/*{ name: 'Bob', lastName: 'Smith' }*/

例子b: 克隆对象

var obj = { person: "Bob Smith"};
var clone = Object.assign({}, obj);
console.log(clone);/*{ person: 'Bob Smith' }*/var test=null;
var test1=Object.assign({},test);
console.log(test1);/*{}*/var test2=undefined;
var test4=Object.assign({},test2);
console.log(test4);/*{}*/

3、Object.create(prototype,descriptors)

var newObj = Object.create(null, {size: {value: "large",enumerable: true},shape: {value: "round",enumerable: true}});document.write(newObj.size + "<br/>");/*large*/
document.write(newObj.shape + "<br/>");/*round*/
document.write(Object.getPrototypeOf(newObj));/*null*/

var firstLine = { x: undefined, y: undefined };var secondLine = Object.create(Object.prototype, {x: {value: undefined, writable: true, configurable: true, enumerable: true},y: {value: undefined, writable: true, configurable: true, enumerable: true}
});document.write("first line prototype = " + Object.getPrototypeOf(firstLine));/*first line prototype = [object Object])*/
document.write("<br/>");
document.write("second line prototype = " + Object.getPrototypeOf(secondLine));/*first line prototype = [object Object]*/

 4、Object.keys(obj) && Object.values(obj)

 5、Object.freeze() && Object.isFrozen()