Map object, Set object using (2)

See what the focus of today Set

Set in my mind it is mainly to heavy, Set is a set of values, this collection of all the values appear only once

Set property size: Map and of the same size, the total number of members returned

Set method:

Set.prototype.add(value): Adding a value to return to Set structure itself.
Set.prototype.delete(value): Delete a value, it returns a Boolean value that indicates whether the deletion was successful.
Set.prototype.has(value): Returns a Boolean value that indicates whether the value is Seta member.
Set.prototype.clear(): Clear all members, no return value.

let set = new Set();
set.add(1);set.add(1);set.add(2);
set.has(1);//true
set.has(2);//true
set.add({x:2});

set.add({x:1});
set.add(function(){});
set.add([]);
set.has(2)//true

console.log(set.size)
set.delete(1);
set.forEach(point =>{
    if(point.x<5){
        set.delete(point)
    }
})
console.log(set.size)//3

set.clear();
console.log(set.size)//0

Set inside a lot of the same Map and methods (including below). Likewise objects, functions, arrays, is unique address,

Set comprising determination has special value

+0 -0 is constant, and there undefned undefined, They is not repeated, and NaN and NaN are not identical, Set They think that equal

Set traversal methods:

Set.prototype.keys(): Returns walker keys.
Set.prototype.values(): Returns the key value walker.
Set.prototype.entries(): Returns all members of the walker.
Set.prototype.forEach(): Through all the members of Set.

const set = new Set(['a', 'b', 'c'])

for (let item of set.keys()) {
  console.log(item)
}
// a
// b
// c

for (let item of set.values()) {
  console.log(item)
}
// a
// b
// c

for (let item of set.entries()) {
  console.log(item)
}
// ["a", "a"]
// ["b", "b"]
// ["c", "c"] 
fordirectly set traversal example, is equivalent to traversing the set values of instance method//
 (let i of set) {
  console.log(i)
}
// a
// b
// c

set.forEach((value, key) => console.log(key + ' : ' + value))

// a: a
// b: b
// c: c

Finally compare the difference

Set mainly to heavy, the only value,

Map predominantly present in the form of key-value pairs, similar to json, but contains all data types

Map object, Set object using (2)

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