JavaScript - Advanced Flashcards
(40 cards)
call()
The call() method invokes a function with a specified this value and arguments provided individually.
For Example:
function greet(name) {
console.log(Hello, ${name}!);
}
greet.call(null, ‘John’);
apply()
The apply() method is similar to call(), but it accepts arguments as an array or an array-like object.
For Example:
function greet(name) {
console.log(Hello, ${name}!);
}
greet.apply(null, [‘John’]);
bind()
The bind() method creates a new function with a specified this value and partially applies arguments.
For Example:
function greet(name) {
console.log(Hello, ${name}!);
}
const greetJohn = greet.bind(null, ‘John’);
greetJohn();
Lexical Scope
Lexical scoping means that the scope of a variable is determined by its location within the source code.
Variables are accessible within their containing functions or blocks.
Dynamic Scope
Dynamic scoping, on the other hand, determines the scope of a variable based on the flow of the program during runtime.
The scope depends on the call stack.
Explain the concept of memoization in JavaScript
Memoization is a technique to cache the results of expensive function calls and return the cached result when the same inputs occur again.
For Example:
function memoize(fn) {
const cache = {};
return function(…args) {
const key = JSON.stringify(args);
if (cache[key]) {
return cache[key];
}
const result = fn.apply(this, args); cache[key] = result; return result; }; }
const fibonacci = memoize(function(n) {
if (n <= 1) {
return n;
}
return fibonacci(n - 1) + fibonacci(n - 2);
});
console.log(fibonacci(5)); // Returns 5
console.log(fibonacci(10)); // Returns 55
How does Memoization improve performance?
It improves performance by avoiding unnecessary computations.
What is the process that JavaScript follows for Memory Management and Garbage Collection?
Allocation
Use
Deallocation
Garbage Collection
Garbage Collection Allocation
When objects are created, memory is allocated to store them.
Garbage Collection Use
Objects are used and referenced by variables or other objects.
Garbage Collection Deallocation
When objects are no longer needed, memory is deallocated to free up resources.
Garbage Collection Step
JavaScript’s garbage collector periodically identifies and removes objects that are no longer reachable, i.e., not referenced by any variables or objects.
Different techniques for optimizing JavaScript code
Minification
Bundling
Caching
Debouncing
Memoization
Minification
Removing unnecessary characters (whitespace, comments) to reduce file size.
Bundling
Combining multiple JavaScript files into a single file to reduce network requests.
Explain the concept of function composition in JavaScript
Function composition is the process of combining multiple functions to create a new function that performs multiple operations.
For Example:
const add = (a, b) => a + b;
const multiply = (a, b) => a * b;
const pipe = (…fns) => (x) => fns.reduce((y, fn) => fn(y), x);
const addAndMultiply = pipe(add, multiply);
console.log(addAndMultiply(2, 3)); // Returns 10 (2 + 3 = 5, 5 * 2 = 10)
What are Web Workers in JavaScript
Web Workers are a browser feature that enables JavaScript code to run in the background on separate worker threads, separate from the main UI thread.
Explain the concept of the prototype chain in JavaScript’s object-oriented programming model.
In JavaScript’s object-oriented programming model, each object has an internal property called the prototype.
The prototype is another object that the current object can inherit properties and methods from.
If a property or method is not found on the current object, JavaScript looks for it in the prototype chain, traversing up the chain until it finds the property or reaches the end (null prototype).
What are the different ways to handle authentication and authorization in JavaScript applications?
JSON Web Tokens (JWT)
OAuth
Session-based authentication
Role-based access control (RBAC)
JSON Web Tokens (JWT)
Storing user authentication information as digitally signed tokens.
OAuth
Delegating user authentication to third-party providers like Google or Facebook.
Session-based authentication
Storing session data on the server and using cookies or session tokens to identify authenticated users.
Role-based access control (RBAC)
Assigning roles to users and granting permissions based on those roles.
What is functional programming, and how can it be applied in JavaScript?
Functional programming is a programming paradigm that emphasizes the use of pure functions, immutability, and higher-order functions.
In JavaScript, functional programming can be applied by using functions as first-class citizens, avoiding side effects, and using higher-order functions for composition and abstraction.
For Example:
// Using map and filter higher-order functions for transformation and filtering
const numbers = [1, 2, 3, 4, 5];
const doubled = numbers.map((n) => n * 2); // [2, 4, 6, 8, 10]
const evenNumbers = numbers.filter((n) => n % 2 === 0); // [2, 4]
// Using reduce to calculate the sum of an array
const sum = numbers.reduce((acc, n) => acc + n, 0); // 15
