Set basic introduction to data structures

structure

const set = new Set([1, 2, 3, 4, 4]);

 Acceptable parameters for all data interface having iterable　　

 

characteristic:

 Similarly array, no duplicate values.

const set = new Set([1, 2, 3, 4, 4]);
[...set] //1,2,3,4

　important point:

       1. Members between duplicate values ​​similar to values ​​determined === ', but a plurality would be judged to be equal NaN

const set = new Set([1,NaN, NaN, 4, '4']);
console.log(...set) 

      2. The two objects are not equal to the total　

const set = new Set([{}, {},{name:'shyno'},{name:'shyno'}]);
console.log(...set)

　　

     3. No key value only

const arr = [1,2,2,3,4,5,5,6]
let obj = {name:'shyno'}
const set = new Set(arr);
const setArr = Array.from(set)
console.log(Object.keys(arr),Object.keys(obj),Object.keys(set))

　　

          (It can be seen key set is empty)

　 4.Set not an array

const set = new Set([{}, {},{name:'shyno'},{name:'shyno'}]);
document.write(set[0])               //undefined
console.log(set.concat([1,2]))     //set.concat is not a function　

         (. 1) Set the array can be used to de-emphasis, however, the need to sub-arrays Set

const set = new Set([1,2,3,3,4,4,5]);
const arr = Array.from(set)
console.log(arr[0],arr.concat(['1','2']))

　　(2) Set may also be used to re-string

const set = new Set('aabbccdee');
const arr = Array.from(set)
console.log(arr[0],arr.concat(['1','2']))

　　

　　(3) Other data interface having iterable duplicate values ​​which can be removed by this method

 

 

Properties and Methods

      Constructors: Set.prototype.constructor

console.log(Set.prototype.constructor)

　　

　　Total length / size / members: Set.prototype.size

ARR = const [1,2,2,3,4,5,5,6] 
const new new SET = the Set (ARR); 
const = setArr Array.from (SET) 
the console.log ( 'original array length', arr. length, 'the total number of members of the set of', set.size, 'set length after transfer array', setArr.length)

　　

        Add members: add () ------ add some value, return Set structure itself

const arr = [1,2,2,3,4,5,5,6]
const set = new Set(arr);
set.add(2)
const setArr = Array.from(set)
console.log(set,set.add('shyno'))

　　

      (Note that the same print out the results, indicating its return value is the set itself)

                Without repeated, different types of data may be added

　　To remove a member: delete () ------ delete a value, it returns a Boolean value that indicates whether the deleted successfully

const arr = [1,2,2,3,4,5,5,6]
const set = new Set(arr);
const setArr = Array.from(set)
console.log(set)
console.log(set .delete(2))
console.log(set)
console.log(set .delete(2))

　　

     (Set no repeat value, so the same operation, only the first will succeed)

　　No presence determination: has (value) ----- returns a Boolean value indicating whether the value is Seta member of

const arr = [1,2,2,3,4,5,5,6]
const set = new Set(arr);
const setArr = Array.from(set)
console.log(set)
console.log(set .has(2))
console.log(set .delete(2))
console.log(set .has(2))
console.log(set)

　　

　　

     (Here, obviously when there is no print set 2, but has (2) is indeed true, the delete operation was false)

　　 Empty members: clear () ----- remove all members, no return value

const arr = [1,2,2,3,4,5,5,6]
const set = new Set(arr);
const setArr = Array.from(set)
console.log(set)
console.log(set .clear())
console.log(set .delete(2))
console.log(set.add(2))
console.log(set .has(2))
console.log(set)