ES6 other syntax and extended syntax summary

Catalog

One 、includes

Two 、** Power operation

3、 ... and 、flat Array dimension reduction

Four 、flat and map A combination of

5、 ... and 、 Object extension method

6、 ... and 、 fromEntries Put the form of key value pairs Turn to object

7、 ... and 、trim Remove the space

8、 ... and 、?. The object level is deep

---

One 、includes

Used to detect whether the array contains an element , Returns a Boolean value .

example ： Judge 2 Whether in arr Array Just go back to true Instead of false.

let arr = [1,2,3];
console.log(arr.includes(2));

Two 、** Power operation

stay ES7 Introducing the exponential operator **, Used to implement power operation , Function and Math.pow The result is the same .

example ：

console.log(10**3);//10*10*10

3、 ... and 、flat Array dimension reduction

let arr = [1,[[2],3],4];
console.log(arr.flat(2)); // Default drop 1 dimension , Parameters ： Specify dimensions 

Four 、flat and map A combination of

let arr = [1,2,3,4];
let newarr = arr.flatMap((item)=>{
	return [item];
})
console.log(newarr);

5、 ... and 、 Object extension method

const Stu = {info:" Class information ",data:[" Zhang San "," Li Si "," Wang Wu "],major:" Computer science "};
console.log(Object.keys(Stu));// Get all the keys 
console.log(Object.values(Stu));// Get all the value 
const arrMap = Object.entries(Stu);// Turn the object into [[key,value],[],[]]
const myMap = new Map(arrMap);
console.log(myMap);

 

realname:{
	value:" Zhang San ",
 	writable:true,// Property is writable 
 	configurable:true,// Properties are not configurable , Delete 
	enumerable:true,// Enumerable or not 
	},
				
 })
    Person.realname = " Li Si ";
    delete Person.realname;// Delete attribute 
    console.log(Person);
			
for(let key in Person){
 	console.log(key);
}

6、 ... and 、 fromEntries Put the form of key value pairs Turn to object

let arr = [["realname"," Zhang San "],["age",19]];
const Person =Object.fromEntries(arr);
console.log(Person);

7、 ... and 、trim Remove the space

 let str = "  abc  ";
 console.log(str);
 console.log(str.trimStart() + "---");
 console.log("---" + str.trimEnd()+"---")
 console.log("---"+str.trim() + "---");

8、 ... and 、?. The object level is deep

 const Person = {
                realname: " Zhang San ",
                info: {
                    sex: " Gender ",
                    height: "180",
                }
            }
            const height = Person?.xxx?.sex;
            console.log(height);