Understanding Programming Concepts

What are the basic data types in JavaScript?

• Undefined, Null, Boolean, Number, BigInt, String, Symbol

• Array, Object, Function

• Date, RegExp, Map

• Byte, Short, Long

Answer explanation

The basic data types in JavaScript include Undefined, Null, Boolean, Number, BigInt, String, and Symbol. These types represent the fundamental building blocks for data manipulation in the language.

Explain the concept of variable scope.

• Variable scope defines the visibility and lifetime of variables in a program, distinguishing between global and local access.

• Variable scope only applies to global variables.

• Variable scope is irrelevant in programming languages.

• Variable scope determines the speed of variable access.

Answer explanation

Variable scope is crucial in programming as it defines where variables can be accessed and how long they exist. The correct choice highlights that it distinguishes between global and local variables, impacting their visibility and lifetime.

What is the difference between == and === operators?

• '===' is used for comparing objects only.

• The '==' operator is for value equality with type coercion, and '===' is for strict equality without type coercion.

• '==' is faster than '===' in all cases.

• '==' checks both value and type equality.

Answer explanation

The '==' operator checks for value equality and allows type coercion, meaning it can compare different types by converting them. In contrast, '===' checks for strict equality, requiring both value and type to be the same.

How do you write an if-else statement in Python?

• if condition then do_something

• if condition: do_something; else do_something_else;

• if (condition) { do_something } else { do_something_else }

• if condition: do_something else: do_something_else

Answer explanation

The correct if-else statement in Python uses colons and indentation. The format 'if condition:\n do_something\nelse:\n do_something_else' clearly shows the structure, making it the right choice.

What is a for loop and how does it work?

• A for loop is a type of variable used in programming.

• A for loop is a method for defining classes in programming.

• A for loop is a function that executes only once.

• A for loop is a programming construct that repeats a block of code a specified number of times or iterates over elements in a collection.

Answer explanation

A for loop is a programming construct that allows code to be executed repeatedly, either for a set number of times or for each element in a collection, making it essential for tasks that require iteration.

Define a function in JavaScript and give an example.

• function subtract(a, b) { return a - b; }

• function multiply(a, b) { return a * b; }

• function divide(a, b) { return a / b; }

• function add(a, b) { return a + b; }

Answer explanation

The function 'add' correctly defines a function in JavaScript that takes two parameters, 'a' and 'b', and returns their sum. This is a clear example of a function that performs a basic arithmetic operation.

What is the Document Object Model (DOM)?

• A markup language for creating web applications.

• A programming language used for server-side scripting.

• A method for styling web pages using CSS.

• The Document Object Model (DOM) is a programming interface that represents the structure of a document as a tree of objects, enabling dynamic manipulation of web pages.

Answer explanation

The correct choice defines the DOM as a programming interface that represents a document's structure as a tree of objects, allowing for dynamic web page manipulation, which is essential for interactive web applications.

List three string methods in Python and their uses.

• find() - Searches for a substring in a string.

• replace() - Changes all occurrences of a substring.

• 1. upper() - Converts string to uppercase. 2. lower() - Converts string to lowercase. 3. strip() - Removes leading and trailing whitespace.

• concat() - Joins two strings together.

Answer explanation

The correct choice lists three string methods: upper() converts to uppercase, lower() converts to lowercase, and strip() removes whitespace. These methods are commonly used for string manipulation in Python.

What is the purpose of the 'let' keyword in JavaScript?

• To declare block-scoped variables.

• To declare global variables.

• To create constants that cannot be changed.

• To define functions in JavaScript.

Answer explanation

The 'let' keyword in JavaScript is used to declare block-scoped variables, meaning they are limited to the block in which they are defined. This is different from 'var', which declares variables globally or throughout the function.

How can you check if a number is even or odd using conditional statements?

• Use 'if (number % 2 == 0) { // even } else { // odd }'

• Use 'if (number == 0) { // even } else { // odd }'

• Check if 'number > 0' for even numbers

• Use 'if (number / 2 == 1) { // odd } else { // even }'

Answer explanation

The correct method to check if a number is even or odd is using 'if (number % 2 == 0) { // even } else { // odd }'. This checks the remainder when dividing by 2: if it's 0, the number is even; otherwise, it's odd.