JavaScript Basics - Study Guide

=== (strict equality operator) compares both values AND types without conversion

Example:

5 == "5" // true (string "5" is converted to number 5) 5 === "5" // false (different types: number vs string)

Closures allow functions to maintain access to variables from their parent scope even after the parent function has finished executing.

Example: javascript function createCounter() { let count = 0; return function() { return ++count; }; }

const counter = createCounter(); counter(); // 1 counter(); // 2 counter(); // 3

In this example, the inner function maintains access to count even after createCounter() has finished executing.

1. Call Stack - Where synchronous code executes
2. Callback Queue - Where callbacks wait to be processed
3. Microtask Queue - Higher priority queue (for Promises)
4. Event Loop - Continuously checks if the call stack is empty, then moves callbacks to the stack

This allows JavaScript to be non-blocking despite being single-threaded.

1. Callbacks:

fetchData(function(error, data) { if (error) handleError(error); else processData(data); });

2. Promises:

fetchData() .then(data => processData(data)) .catch(error => handleError(error));

3. Async/Await (ES2017):

async function getData() { try { const data = await fetchData(); processData(data); } catch (error) { handleError(error); } }

Async/await is built on promises and provides the most readable syntax.