ES6 Symbol类型 附带:Proxy和Set

七种数据类型

·Symbol 

·undefined

·null

·Boolean

·String

·Number

·Object

 

let a = Symbol('this is a symbol');

let b = Symbol();

console.log(a === b); //false

 

 

Symbol的用途:在{ }作用域内可以临时重写一个变量

 

//

//file1.js

let name = Symbol();

{

var person = { };

person[name] = 'File1';

console.log("person[name]",person[name]);

}

 

//file2.js

{

let name = Symbol();

person[name] = 'File2';

//可以在局部变量{ }里临时重写，但是在全局内不变

console.log('person[name]',person[name]);

 

}

console.log('person[name]',person[name]);

 

 

 

 

Proxy 代理

var user = new Proxy({},{

get:function(obj,prop)

{

if(prop == 'fullname')

return obj.fname + ' ' + obj.lname;

},

/*

set:function(obj,prop){

}

*/

})

user.fname = 'Bob';

user.lname = 'Wood';

console.log("user.fullname:",user.fullname);

console.log("user.age:",user.age);

 

 

set

 

var arr = [1,2,3,3];

var s = new Set([1,2,3,3]);

s.add(4);

console.log("s.size",s.size);

console.log("s:",s);

s.delete(2);

console.log("s",s);

console.log("s.has(5)",s.has(5));

s.has(5);