function curryFunction(a) {
  return function (b) {
    const res = a + b
    return function (c) {
      return res + c
    }
  }
}
console.log(curryFunction(1)(2)(3))

To check if an object is null or not: _.isEmpty(obj) ? true : false; - optimized approach

Array.prototype.last = function() {
    return this.length == 0 ? -1 : this[this.length - 1];
};

/**
 * const arr = [1, 2, 3];
 * arr.last(); // 3
 */

1. Array.prototype.last:
   • This code adds a method called last to the Array.prototype. This means that all arrays will inherit this method and can call it directly.

What is Lexical Environment?

A lexical environment is the internal structure that JavaScript creates at runtime to keep track of:

• All local variables
• A reference to its outer (parent) environment

It's created whenever a function is invoked or a block is entered.

Example:

js
CopyEdit
function outer() {
  let x = 10;

  function inner() {
    console.log(x); // ❓ How does this work?
  }

  return inner;
}

const fn = outer(); // outer is done, but...
fn(); // still logs 10

Here’s what’s happening:

• inner() has a lexical environment that references the outer function's environment.
• That environment still "remembers" the variable x = 10, even after outer() has returned — this is called a closure.

memory management

JavaScript automatically allocates and deallocates memory using Garbage Collection (GC) mechanisms.

https://www.geeksforgeeks.org/memory-management-in-javascript/

functional prog

Functional programming is a declarative programming paradigm that treats computation as the evaluation of mathematical functions and avoids changing state and mutable data. In JavaScript, it emphasizes the use of pure functions, immutability, and higher-order functions. [[1](https://medium.com/@rashmipatil24/functional-programming-in-javascript-bfc7f53b77a1#:~:text=Functional programming (FP) is a programming paradigm,its simplicity%2C maintainability%2C and ease of testing.)]