Javascript Symbol Type

Introduction

Javascript Symbol data type are primitive values.

Symbol instances are unique and immutable.

A symbol can be a unique identifier for object properties that does not risk property collision.

Create

Symbols are instantiated using the Symbol function.

typeof operator will identify a symbol as symbol. 

let sym = Symbol(); 
console.log(typeof sym);  // symbol

Symbol() function can have an optional string used for identifying the symbol instance when debugging.

The string you provide is separate from the symbol's identity: 

let genericSymbol = Symbol(); 
let otherGenericSymbol = Symbol(); 
 
let fooSymbol = Symbol('foo'); 
let otherFooSymbol = Symbol('foo'); 
              /*  ww w  .ja  v  a2s.c  om*/
console.log(genericSymbol == otherGenericSymbol);  
console.log(fooSymbol == otherFooSymbol);          // false

Symbols do not have a literal string syntax. 

let genericSymbol = Symbol(); 
console.log(genericSymbol);  // Symbol() 
              // w w w.j  a  v a  2  s. co  m
let fooSymbol = Symbol('foo'); 
console.log(fooSymbol);      // Symbol(foo);

The Symbol function cannot be used with the new keyword. 

let mySymbol = new Symbol();  // TypeError: Symbol is not a constructor

To use an object wrapper, make use of the Object() function: 

let mySymbol = Symbol(); 
let myWrappedSymbol = Object(mySymbol); 
console.log(typeof myWrappedSymbol);  // "object"



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