Object Method summary

1、Object.entries()

Object.entries () can be a key object to traverse an array out, and the results for ... in ... the same, but does not traverse the prototype property

Examples a: --- incoming object 

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

Example b: --- incoming array

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

Example c: --- incoming array containing objects

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

Examples of d: --- all incoming array of objects

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

Examples e: --- incoming string

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

Examples f: --- incoming numbers, floating point numbers

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

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

Examples g: --- into the Object 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,...)

This method only copy source attribute object itself, not copied inherited attributes.

Object.assign method of implementation is shallow copy, rather than a deep copy. That is, the value of a property if the source object is an object, then get a copy of the target object is a reference to the object. Property of the same name will be replaced. 
Object.assign only copies the value, the value if you want to copy is a function of the value, then evaluated and then copied. 
Object.assign can be used to handle an array, but the array will treated as an object. 

{X = target const: 0, Y:. 1 }; 
const Source = {X:. 1, Z: 2, Fn: {Number:. 1 }}; 
the console.log (Object.assign (target, Source)); 
// target {x: 1, y: 1, z: 2, fn: {number: 1}} // attribute with the same name will be overwritten 
target.fn.number = 2 ; 
the console.log (Source) // Source {X:. 1 , z: 2, fn: { number: 2}} // copy the object reference

function the Person () {
   the this .name =. 1 
}; 
Person.prototype.country = 'China' ;
 var Student = new new the Person (); 
student.age = 29 ; 
const Young = {name: 'Zhang' }; 
Object.assign (Young, Student); 
// Young {name: 'Zhang', Age: 29} // copy only own properties, can not be copied prototype

Object.assign ([1, 2, 3], [4, 5])                       // the array as an object to handle 
// [4, 5, 3] 

// {0: 1, 1: 2, 2: 3 } {0: 4, 1: 5}

Examples of a: Combine Objects

var first = { name: "Bob" };
var last = { lastName: "Smith" };

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

Examples of b: clone

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()