Javascript - Data Types Using Symbols
Introduction
Symbols are mainly used as unique property keys because a symbol can never clash with any other property.
Consider the following example, where we have an object Person with some "public" properties:
let Person = {
name: "John",
age: 14,
location: "New York"
}
Now let's suppose we want to add a private method to the Person object. We can do that using Symbols as follows:
Demo
let votingEligibility = Symbol();
let Person = { /* w w w . ja v a2s.com*/
name: "John",
age: 14,
location: "New York"
}
Person[votingEligibility] = function() {
return this.age >= 18;
}
console.log(Person);
Result
You can see that an anonymous method has been added to it.
You can use computed property keys here:
let Person = {
name: "John",
age: 14,
location: "New York",
[Symbol()]: function() {
return this.age >= 18;
}
}
The Symbol property is non-enumerable and anonymous.
Therefore, when using the for...in loop, symbol properties of the object won't be accessible while traversing.
You can get the Symbol property using Object.getOwnPropertySymbols(). For example:
Object.getOwnPropertyNames(Person); // ["name", "age", "location"] Object.getOwnPropertySymbols(Person); // [Symbol()]
Here is how you would use Object.getOwnPropertySymbols() in the previous example where we created the Person object.
let canVote = Object.getOwnPropertySymbols(Person)[0];
Person[canVote](); // false
You can achieve this by using the reference created to bind the property with the Person object.
Person[votingEligibility](); // false