The first part ：Set data structure ：

ES6 Provides a new data structure  Set. It's like an array , But the values of the members are unique , There are no duplicate values .

Definition ：const s = new Set();

initialization ：const set = new Set([1, 2, 3, 4, 4]);//{1, 2, 3, 4}

Example method ：

const s = new Set();

s.add(1).add(2);// add value

s.delete(2);// Delete value , It's not an index

console.log(s.has(2));//set Yes no 2, There is a return true

console.log(s.clear());// Clear all values

  The second part ：Array Common objects of

1,array Extension method of   Processing first and then returning a new array

       // Array map()
             // let arr= [1,2,3,4]
             // let newarray = arr.map((item)=>{
                //  return item + 2;
             // })
             // console.log(newarray)

The result is ：

0: 3

1: 4

2: 5

3: 6

length: 4

1： Find the maximum value in the array ( cut )

            let arr = [1,2,3,4,5]
             let newarray = arr.reduce((total,values)=>{
                 return total<values?values:total;
             })
             console.log(newarray)

  The final result is ： The maximum value is 5

2, Array filter() 

        // let arr = [1,2,3,4,5,6]
             // let newarray = arr.filter((item)=>{
                //  return  item > 5;
             // })
             // console.log(newarray)

  // The final return value is 6

  4:fill fill ( Usage is ('x',1,3) first x Indicates the content after replacement   The second acquisition parameter is from which position   The third value refers to the end of the third digit ( But it does not include the current bit ))

             // let arr = [1,2,3,4,5]
              // arr.fill('x',1,3);
              // console.log(arr)

  // The final return value is 1,x,x,4,5

The third part ： Other methods

 1,in Determine whether the element is an array ( object ) Properties of

 // let arr = ['a','b','c','d']
             // console.log(a in arr);// The return is false Non placed here a It's the subscript of the array element , If you place the subscript of the element, you can print
             // let arr = ['a','b','c','d']
             // console.log(4 in arr)

// The return is true

 2,some() Method is used to detect whether the elements in the array meet the specified conditions （ Function provides ）

              / / var ages = [3, 10, 1, 1];
             // var flag = ages.some(v=> v>2);
             // console.log(flag);

 // The final result is true

3:split Put the string according to “ Separator ” Converted to an array   join Divide the array into “ Separator ” Concatenate into a string

// let arr = 'abcde';
            // let arr1 = arr.split('');
            // console.log(arr1);
            // // The output is  ['a', 'b', 'c', 'd', 'e']
         //    let arr2 = arr1.join('-');
            // console.log(arr2);
            // The output is  a-b-c-d-e

4:Array.of Responsible for the A pile of text is converted into an array

      // let a=1;
            // let b=2;
            // let c=3;
            // let arr1 = Array.of(a,b,c);
            // console.log(arr1);

The final result ： [1, 2, 3]