Functions in Programming
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Questions and Answers

What is the purpose of a function?

  • To execute a block of code multiple times from different parts of a program (correct)
  • To create a new object
  • To store a collection of values
  • To declare a variable

    • What is the difference between a function declaration and a function expression?

  • A function declaration is defined with a name, while a function expression is anonymous (correct)
  • A function declaration is hoisted, while a function expression is not
  • A function declaration can take arguments, while a function expression cannot
  • A function declaration returns a value, while a function expression does not

    • What is the purpose of the push() method in an array?

  • To add one or more values to the end of the array (correct)
  • To create a new array from a subset of an existing array
  • To remove the first value from the array
  • To remove the last value from the array

    • What is the difference between indexOf() and includes() methods in an array?

    <p><code>indexOf()</code> returns the index of the value, while <code>includes()</code> returns a boolean</p> Signup and view all the answers

    What is the purpose of the map() method in an array?

    <p>To create a new array by applying a function to each value in an existing array</p> Signup and view all the answers

    What is the scope of a variable defined inside a function?

    <p>Local scope</p> Signup and view all the answers

    What is the purpose of the splice() method in an array?

    <p>To add or remove values from a specific position in the array</p> Signup and view all the answers

    What is the purpose of hoisting in functions?

    <p>To allow functions to be called before they are defined</p> Signup and view all the answers

    What is the default scope of a variable declared outside a function or block scope?

    <p>Global</p> Signup and view all the answers

    Which of the following is a characteristic of variables declared with let and const?

    <p>They are not hoisted to the top of their scope</p> Signup and view all the answers

    What is the purpose of the prototype chain in object-oriented programming?

    <p>To inherit properties from a parent object</p> Signup and view all the answers

    What is the primary difference between a function declaration and a function expression?

    <p>The way they are declared</p> Signup and view all the answers

    What is a closure in the context of functions?

    <p>A function that has access to its own scope and the scope of its parent functions</p> Signup and view all the answers

    Which of the following is an example of a primitive type in JavaScript?

    <p>String</p> Signup and view all the answers

    What is the purpose of a constructor in object-oriented programming?

    <p>To initialize an object with default values</p> Signup and view all the answers

    Which of the following is an example of a reference type in JavaScript?

    <p>Object</p> Signup and view all the answers

    Study Notes

    Functions

    • A block of code that can be executed multiple times from different parts of a program
    • Can take arguments, which are values passed to the function when it's called
    • Can return values, which can be used by the code that called the function
    • Can be defined with a name, or anonymously
    • Types of functions:
      • Function declaration: function name(parameters) { code }
      • Function expression: const name = function(parameters) { code }
      • Arrow function: const name = (parameters) =&gt; { code }
    • Function scope: variables defined inside a function are only accessible within that function
    • Hoisting: function declarations are moved to the top of their scope, allowing them to be called before they're defined

    Arrays

    • A data structure that stores a collection of values
    • Values can be of any type, including strings, numbers, and objects
    • Indexed, meaning each value has a unique index or key
    • Can be created using the [] syntax or the Array constructor
    • Methods:
      • push(): adds one or more values to the end of the array
      • pop(): removes the last value from the array and returns it
      • shift(): removes the first value from the array and returns it
      • unshift(): adds one or more values to the beginning of the array
      • splice(): adds or removes values from a specific position in the array
      • indexOf(): returns the index of the first occurrence of a value in the array
      • includes(): returns a boolean indicating whether a value is in the array
    • Array manipulation:
      • Concatenation: combining two or more arrays using the spread operator (...)
      • Slicing: creating a new array from a subset of an existing array using the slice() method
      • Mapping: creating a new array by applying a function to each value in an existing array using the map() method
      • Filtering: creating a new array by selecting values from an existing array that meet a certain condition using the filter() method
      • Reducing: reducing an array to a single value by applying a function to each value using the reduce() method

    Functions

    • A block of code that can be executed multiple times from different parts of a program, allowing for code reuse and modularity.
    • Functions can take arguments, which are values passed to the function when it's called, and use them to perform calculations or operations.
    • Functions can also return values, which can be used by the code that called the function, allowing for more complex logic and data flow.
    • Functions can be defined with a name, or anonymously, and can be assigned to variables or passed as arguments to other functions.
    • There are three types of function definitions: function declaration, function expression, and arrow function, each with its own syntax and use cases.

    Arrays

    • A data structure that stores a collection of values, which can be of any type, including strings, numbers, and objects.
    • Arrays are indexed, meaning each value has a unique index or key, allowing for efficient access and manipulation.
    • Arrays can be created using the [] syntax or the Array constructor, and can be manipulated using various methods.
    • Array methods include:
      • push(): adds one or more values to the end of the array.
      • pop(): removes the last value from the array and returns it.
      • shift(): removes the first value from the array and returns it.
      • unshift(): adds one or more values to the beginning of the array.
      • splice(): adds or removes values from a specific position in the array.
      • indexOf(): returns the index of the first occurrence of a value in the array.
      • includes(): returns a boolean indicating whether a value is in the array.
    • Arrays can be manipulated using various techniques, including:
      • Concatenation: combining two or more arrays using the spread operator (...).
      • Slicing: creating a new array from a subset of an existing array using the slice() method.
      • Mapping: creating a new array by applying a function to each value in an existing array using the map() method.
      • Filtering: creating a new array by selecting values from an existing array that meet a certain condition using the filter() method.
      • Reducing: reducing an array to a single value by applying a function to each value using the reduce() method.

    Variables

    • Variables are declared using the let, const, and var keywords.
    • JavaScript has two main types of variables: Primitive and Reference.
    • Primitive types include number, string, boolean, null, undefined, and symbol.
    • Reference types include object, array, and function.
    • Variables have a scope, which determines their accessibility.
    • Global variables are declared outside a function or block scope.
    • Local variables are declared inside a function or block scope.
    • Variables declared with var are "hoisted" to the top of their scope.
    • Variables declared with let and const are not "hoisted".

    Functions

    • Functions are declared using the function keyword.
    • There are two main types of functions: Function Declaration and Function Expression.
    • Function Declaration is a function declared as a separate statement.
    • Function Expression is a function declared as an expression, often assigned to a variable.
    • Functions can take arguments, which are passed when the function is called.
    • Functions can return a value using the return statement.
    • A function has access to its own scope and the scope of its parent functions, creating a closure.
    • Arrow Functions are a concise way to declare functions, introduced in ECMAScript 6 (ES6).

    Object-Oriented Programming (OOP)

    • Objects are collections of key-value pairs, created using the {} syntax.
    • Properties are the key-value pairs within an object.
    • Methods are functions within an object, used to perform actions on the object.
    • Inheritance is the process of creating a new object based on an existing object, using the prototype chain.
    • Constructors are special functions used to create new objects, often with the new keyword.
    • Prototypes are objects that serve as a blueprint for other objects, allowing for inheritance and method sharing.
    • The this keyword refers to the current object being executed, often used in methods and constructors.

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    Understand the concept of functions in programming, including declarations, expressions, and arrow functions. Learn about function arguments and return values.

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