30 Asked Interview Questions and Answers (2024)

Symbols are a new primitive data type in ES6, used to create unique identifiers.

Example:

const mySymbol = Symbol('description');

A Set is a collection of values with no duplicate entries. It is iterable and can store various types of values.

Example:

const uniqueNumbers = new Set([1, 2, 3, 2, 1]);

WeakMap and WeakSet are similar to Map and Set, respectively, but they allow for garbage collection of keys and values that are not used elsewhere.

Example:

let weakMap = new WeakMap(); let obj = {}; weakMap.set(obj, 'some value');

The Proxy object is used to define custom behavior for fundamental operations (e.g., property lookup, assignment, enumeration, etc.).

Example:

const handler = { get: function(target, prop) { return prop in target ? target[prop] : 'Not found'; } }; const proxy = new Proxy({}, handler);

The Reflect object provides methods for interceptable JavaScript operations. It is used for method invocation, property manipulation, etc.

Example:

Reflect.has(obj, 'property');

ES6 Interview Questions and Answers