INOTE

What is Symbol in JS?

In JavaScript, a Symbol is a unique and immutable primitive data type introduced in ES6 (ECMAScript 2015). It is often used as a key for object properties to ensure that the property is unique and does not conflict with other property keys, even if they have the same name.

const sym1 = Symbol("description");
const sym2 = Symbol("description");

console.log(sym1 === sym2); // false (Each Symbol is unique)


Key Features of Symbol

  1. Uniqueness: Each Symbol value is unique, even if created with the same description.
  2. Immutability: Once created, the value of a Symbol cannot be changed.
  3. Non-enumerability: Properties keyed by Symbols are not included in for...in loops or Object.keys().
  4. Customizing Built-in Behavior: Override default behavior using well-known Symbols like Symbol.toStringTag to override the toString method.
const obj = {
  [Symbol.toStringTag]: "CustomObject",
  name: "Example"
};

console.log(obj.toString()); // "[object CustomObject]"


Global Symbol Registry

Symbols can be registered in a global registry using Symbol.for(). These are not unique; they can be shared and retrieved globally using the same key.