JavaScript Course in Chennai

var is function-scoped and permits redeclaration, which can lead to problems. In contrast, let and const are block-scoped. let allows the variable’s value to be updated later, whereas const declares a variable with a fixed value that cannot be changed.

Instead of attaching multiple event listeners to each child element, event delegation uses one listener on the parent element. When an event happens on a child, it bubbles up to the parent, making event handling more efficient and faster.

The event loop manages the execution order by keeping track of functions to run. It lets JavaScript handle tasks like fetching data without stopping other code, by waiting until the current code finishes before running waiting tasks.

Promises give a clean way to manage tasks that take time, like server requests. They let you write code that reacts when a task finishes successfully or fails, avoiding deeply nested callbacks and making the flow easier to understand.

== compares two values after trying to convert their types, which can cause mistakes. === compares both the type and value exactly, so it is safer and usually preferred to prevent unexpected bugs.

To keep variables from interfering with each other, use block scope (let and const), wrap code in functions or modules, and avoid declaring global variables unless necessary. This keeps code cleaner and reduces errors.

Modules split code into separate files that each have their own space for variables and functions. This helps organize the code, makes it easier to maintain, and prevents different parts of the program from accidentally affecting each other.

JavaScript moves variable and function declarations to the top of their scope before running code. Variables declared with var are set to undefined at the start, but let and const are not available until their line is reached, which can cause errors if accessed too early.

async/await lets you write code that waits for promises to finish in a way that looks like normal, straight-line code. This makes it easier to read and handle errors compared to chaining .then() calls with promises.