This is the first day of my participation in Gwen Challenge

1. Object.assign()

Used to clone

var first = {name : 'kong'};
var last = {age : 18};
var person = Object.assign(first, last);
console.log(person);//{name : 'kong', age : 18}
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2. Object.is()

Used to determine whether two values are the same

Object.is(a, b); // Return true or false
// Note that, unlike the == operator, this function does not cast any type,
// It should be more like ===, but it's worth noting that it treats +0 and -0 as different
Object.is(+0, -0)  // false
Object.is(NaN.NaN)  // true
Object.is(NaN.0/0)  // true
+0= = = -0 // true
NaN= = =NaN // false
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3. Object.keys()

The name used to return the enumerable properties and methods of the object

var a = {name : 'kong'.age : 18.func : function(){}};
Object.keys(a); //['name', 'age', 'func']
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4. isPrototypeOf()

Determines whether an object exists in the prototype chain of another object

function a(){}
var b = new a();
console.log(a.prototype.isPrototypeOf(b)); //true
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5. Object.defineProperty()

Hijack the set and GET methods of variables, add attributes to objects, or modify the properties of existing attributes

var a = {};
Object.defineProperty(a, 'name', {
	value : 'kong'.enumerable : true	// Whether the attribute is enumerable
})
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6. Object.getOwnPropertyNames(obj)

Returns an array of the property names of all of the object’s own properties, including properties that are not enumerable but do not include the Symbol value as a name

var obj = { 0: "a".1: "b".2: "c"};
console.log(Object.getOwnPropertyNames(obj).sort()); / / / "0", "1", "2"]
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7. Check whether an attribute exists in the object

  1. Use the in keyword
var person = {
	name:'Ming'.age:18
}
console.log('age' in person)	// true has its own property
console.log('address' in person)	// false
console.log('toString' in person) 	// true is an inherited property
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  1. Using the object’s hasOwnProperty() method (recommended)
var person = {
	name:'Ming'.age:18
}
console.log(person.hasOwnProperty('age'))	// true
console.log(person.hasOwnProperty('address'))	// false 
console.log(person.hasOwnProperty('toString'))	// false This is an inherited property, but not its own property
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  1. Use undefined
 // Attribute and inherited attribute can be judged
 var person = {
	name:'Ming'.age:18
}
console.log(person.age ! = =undefined)	// true
console.log(person.address ! = =undefined)	// false
console.log(person.toString ! = =undefined)	// true
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There is a problem with undefined. If the value of the attribute is undefined, the method cannot return the desired result, as follows:

var person = {
	name:'Ming'.age:undefined
}
console.log(person.age ! = =undefined)	// The false attribute exists, but the value is undefined
console.log(person.address ! = =undefined)	// false
console.log(person.toString ! = =undefined)	// true
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4. Check in conditional statements

var person = {}
if(person.age){
	person += 1
}
// If age is undefine, NULL,false," ",0, or NaN, it will remain unchanged
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8. Check whether the object is empty

  1. Using Object.keys(obj) in ES6
var data = {};
var arr = Object.keys(data);
console.log(arr.length == 0); // true is null, false is not null
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  1. Convert the JSON object to a JSON string and determine if the string is “{}”
var data = {};
var b = (JSON.stringify(data) == "{}");
console.log(b);   //true is null, false is not null
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9.

var obj1 = {
    name:' '.age:' '.city:'wuhan'.sex:' ',}var obj2 = {
    name:' '.city:'nanjing'.sex:'male'
}
Object.keys(obj2).forEach(key= >{
    obj1[key] = obj2[key]
})
console.log(obj1,obj2) / / {age: "', city: 'nanjing' name:", "sex:" male "} {city: 'nanjing' name: ", "sex:" male "}
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