JavaScript In Practice: ES6 And Beyond/

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Symbol

Symbol

symbol - a new ES6 primitive type and its use cases

We'll cover the following...

ES6 introduces a new primitive type for JavaScript: Symbols. The global Symbol() function creates a JavaScript symbol. Each time the Symbol() function is called, a new unique symbol is returned.

Node.js
let symbol1 = Symbol();
let symbol2 = Symbol();
console.log( symbol1 === symbol2 ); 
//> false

Symbols don’t have a literal value. All you should know about the value of a symbol is that each symbol is treated as a unique value. In other words, no two symbols are equal.

A symbol is a new type in JavaScript.

Node.js
console.log( typeof symbol1 );
//> "symbol"

Symbols are useful, because they act as unique object keys.

Node.js
let myObject = { 
    publicProperty: 'Value of myObject ["publicProperty"]'
};
myObject[ symbol1 ] = 'Value of myObject [symbol1]';
myObject[ symbol2 ] = 'value of myObject [symbol2]';
console.log( myObject );
//> Object
//>    publicProperty: "Value of myObject[ "publicProperty" ]"
//>    Symbol(): "Value of myObject[ symbol1 ]"
//>    Symbol(): "value of myObject[ symbol2 ]"
//>    __proto__: Object
console.log( myObject[ symbol1 ] );
//> Value of myObject[ symbol1 ]

When console logging myObject inside the Chrome Developer Tools, you can see that both symbol properties are stored in the ...