Junior JavaScript Interview Questions

ES6 modules allow splitting code into separate files using export and import.

• Better code organization
• No global namespace pollution
• Supports tree shaking for optimized builds

Default export: One per module, imported without braces.

Named export: Multiple per module, imported using braces.

Template literals use backticks for interpolation and multi-line strings.

Tagged templates allow processing template literals with custom functions.

Destructuring extracts values from arrays or objects into variables.

Rest (...): collects remaining elements.

Spread (...): expands iterable elements.

Allows functions to use default values when arguments are missing.

Arrow functions inherit this from the surrounding scope, making them ideal for callbacks.

var: function-scoped.

let: block-scoped.

const: block-scoped, cannot reassign.

Promises represent async completion. Chaining uses .then() and .catch() for sequential workflow.

async functions return promises. await pauses execution until promise resolves.

Microtasks: Promises, queueMicrotask.

Macrotasks: setTimeout, setInterval, I/O.

The event loop manages asynchronous execution, processing synchronous code, microtasks, then macrotasks.

Shallow copy: top-level copy.

Deep copy: recursive copy without shared references.

Symbol is a unique primitive used for unique object keys and meta-programming.

Set: stores unique values.

Map: stores key-value pairs with any type of key.

Store weak references to objects, allowing garbage collection. Useful for memory-sensitive caching.

Generators pause/resume execution using yield. Useful for lazy evaluation and iterators.

Modules have their own scope; global scripts share the global namespace.

Use .catch() with promises and try/catch with async/await.

JavaScript uses automatic garbage collection. Developers must avoid leaks by cleaning listeners, closures, and timers.