set，map

1. set

   . 1  {
    2      the let List = new new the Set ();
    . 3      List.add (. 5); // SET additive elements with the Add 
   . 4      List.add (. 7 );
    . 5      the console.log ( 'size', list.size)   // Get length 2 
   . 6  }
    7  {
    8      // can be set directly to the initialization 
   . 9      the let ARR = [1,2,3,4,5 ];
    10      the let List = new new the set (ARR);
    . 11      the console.log ( 'size', List .size)   // . 5 
   12 is }

   The value set is the only application: an array of de-duplication

   . 1  {
    2      the let List = new new the Set ();
    . 3      List.add (. 1 );
    . 4      List.add (2 );
    . 5      List.add (. 1 );   
    . 6      the console.log ( 'List' , List)  
    . 7  
   . 8      the let arr2 is = [1,2,3,2,1];   // string is not automatically converted, and 2 '2' is not the same value, not to the weight 
   . 9      the let List2 = new new the Set (arr2 is);
    10      Console. log ( 'List2', List2)     // l, 2,3 
   . 11 }

   Add, remove, remove, contain

   1 {
   2     let arr = ['add','delete','clear','has'];
   3     let list = new Set(arr);
   4     console.log('has',list.has('add'))
   5     console.log('delete',list.delete('add'),list)
   6     list.clear();
   7     console.log(list)
   8 }

   Traversal

    1 {
    2     let arr = ['add','delete','clear','has'];
    3     let list = new Set(arr);
    4      for(let key of list.keys()){
    5          console.log('key',key)
    6      }
    7      for(let value of list.values()){
    8          console.log('value',value)
    9      }
   10      for(let [key,value] of list.entries()){
   11          console.log('entries',key,value)
   12      }
   13 
   14      list.forEach(item=>{console.log(item)})
   15 }

2. map

   . 1  {
    2      // Map 
   . 3      the let Map = new new the Map ();
    . 4      the let ARR = [ '123' ];
    . 5  
   . 6      map.set (ARR, 456); // Map SET additive elements, to key, value added, key can be any type 
   . 7      the console.log (Map, as map.get (ARR))   // Get GET 
   . 8  }
    . 9  
   10  {
    . 11      the let Map = new new the Map ([[ 'A',. 1], [ 'B', 2 ]])    // Note format 
   12 is      the console.log (Map)
    13 is      the console.log ( 'size' , map.size)
    14      the console.log ( 'Delete', Map. Delete('a'),map)
   15     console.log('clear',map.clear(),map)
   16 
   17 }

    

3. WeakSet，WeakMap

   . 1  {
    2      // weakSet only data objects is weak reference is not detected elsewhere not used 
   3      // no clear method can not traverse, there is no size attribute 
   . 4      the let weakList = new new WeakSet ();
    . 5      the let Arg = {};
    . 6      weakList.add (Arg);
    . 7      the console.log (weakList)
    . 8  }
    . 9  {
    10      // Key values received only WeakMap object no Clear, can not traverse 
   . 11      the let WeakMapList = new new WeakMap ();
    12 is      the let O = {};
    13 is      WeakMapList.set (O, 123 );
    14      the console.log (WeakMapList)
    15 }

    

4. Comparative map, set and array of　　

    Array comparative map

   1  {
    2      // horizontal comparison data structures, CRUD 
   . 3      the let Map = new new the Map ();
    . 4      the let Array = [];
    . 5      // increase 
   . 6      map.set ( 'T', 1 );
    . 7      Array.push ( T {:. 1 });
    . 8      console.info ( 'increase' , Map, Array)
    . 9  
   10      // search 
   . 11      the let map_exist = map.has ( 'T');   // to true 
   12 is      the let array_exist = array.find (Item => item.t); // returns the current value 
   13 is      console.info ( 'check' , map_exist, array_exist)
    14  
   15     // change 
   16      map.set ( 'T', 2 );
    . 17      Array.ForEach (Item => item.t item.t = 2:? '');   // determines if the value is present, modification, there is no without modification 
   18 is      console.info ( 'change' , Map, Array)
    . 19  
   20 is      // delete 
   21 is      Map. Delete ( 'T' )
    22 is      the let index = array.findIndex (Item => item.t); // Find element the subscript location 
   23 is      Array.splice (index,. 1);   // delete the element at the location 
   24      console.info ( 'delete' , Map, Array)
    25  
   26 is }

   Comparative set and Array

    1 {
    2     let set = new Set();
    3     let array= []; 
    4     // 增
    5     set.add({t:1});
    6     array.push({t:1});
    7     console.info('add',set,array)
    8 
    9     //查
   10     let setExist = set.has({t:1});
   11     let arrayExist = array.find(item=>item.t)
   12     console.info('get',setExist,arrayExist)
   13 
   14     // 改
   15     set.forEach(item=>item.t?item.t = 3 : '');
   16     array.forEach(item=>item.t?item.t = 3 :'');
   17     console.info('update',set,array)
   18 
   19     // 删
   20     set.forEach(item=>item.t?set.delete(item.t):'')
   21     let index = array.findIndex(item => item.t);
   22     array.splice(index,1);
   23     console.info('delete',set,array)
   24 }

5. Comparative map, set with object of

    1 {
    2     //map set object 对比
    3     let item = {t:1};
    4     let map = new Map();
    5     let set = new Set();
    6     let obj = {};
    7 
    8     // 增
    9     map.set('t',1);
   10     set.add(item);
   11     obj['t'] = 1;
   12 
   13     console.info('add',map,set,obj)
   14 
   15     // 查
   16     console.table({
   17         map_exist:map.has('t'),
   18         set_exist:set.has(item),
   19         obj_exist:'t' in obj      //对象用in查找
   20     })
   21 
   22     // 改
   23     map.set('t',2);
   24     item.t=2;
   25     obj['t']=2;
   26     console.log('update',map,set,obj)
   27 
   28     // 删
   29     map.delete('t');
   30     set.delete(item);
   31     delete obj['t'];
   32     console.info('delete',map,set,obj)
   33 }