What are Symbols and what are their use cases?

Symbol is a primitive data type introduced in ES6 that creates unique and immutable values. Each Symbol value is guaranteed to be unique, even if they have the same description.

     const sym1 = Symbol('description');
     const sym2 = Symbol('description');
     console.log(sym1 === sym2); // false
     

Common use cases:

1. Creating unique property keys:

        const id = Symbol('id');
        const obj = {
          [id]: 12345,
          name: 'John'
        };
        console.log(obj[id]); // 12345
        

1. Preventing property name collisions:

        const myLib = {
          [Symbol('internal')]: 'private data',
          publicMethod() {}
        };
        

1. Implementing well-known symbols (Symbol.iterator, Symbol.toStringTag, etc.):

        class Collection {
          *[Symbol.iterator]() {
            yield 1;
            yield 2;
          }
        }
        

Note: Symbol properties are not enumerable in for...in loops or Object.keys(), making them useful for metadata and internal object properties.