JavaScript Variables and Data Types Quiz

Variables and Data Types

• Variables in JavaScript can be declared with let (reassignable) and const (non-reassignable).
• Example of variable declaration: let country = 'Nigeria'.
• JavaScript data types include strings, numbers (integer or float), booleans (true/false), undefined, objects, and symbols.

Constants and Reassignment

• const variables must be initialized at declaration and cannot be reassigned.
• Example: const colour = 'red' will throw an error on reassignment such as colour = 'yellow'.

String Concatenation and Template Literals

• Strings are concatenated using the + operator.
• Example: console.log(country + ' has a population of ' + population + '.');
• Template literals, enclosed in backticks (``), support multi-line strings and easy variable interpolation.
• Example: console.log(countryisacountryin{country} is a country in countryisacountryin{continent} and has a population of ${population}.);

Calculating Body Mass Index (BMI)

• BMI calculation formula: mass divided by the square of height.
• Example: const BMIJonas = massJonas / heightJonas ** 2;
• BMI comparison using boolean expressions.
• Example: const markHigherBMI = BMIMark > BMIJonas;

Conditional Statements

• if statements allow for conditional execution of code.

• Basic structure of an if-else statement:

  if (condition) {
      // code to execute if true
  } else {
      // code to execute if false
  }
  

Type Conversion and Coercion

• Type conversion: explicitly changing a variable's type using functions like Number().
• Type coercion: automatic conversion during operations; e.g., subtracting strings converts them to numbers: '23' - '10' equals 13.

Truthy and Falsy Values

• Falsy values include: 0, undefined, null, NaN, and empty strings ('').
• Truthy values are all other values, such as 100, 'Jonas', and empty objects ({}).

Switch Case Statements

• Switch statements enable multi-branch execution based on a variable's value.
• Syntax involves defining cases with corresponding actions and a default case for unhandled values.

Ternary Operators

• Ternary operators offer a concise syntax for if-else statements.
• Example: const allowed = ageDrink >= 18 ? 'wine' : 'water'; determines drink eligibility based on age.

Practical Input Handling

• The prompt-sync module facilitates synchronous user input in Node.js for interactive data gathering.
• Example: const ageDrink = prompt('How old are you?'); captures user age input.

Variables and Data Types

• Variables in JavaScript can be declared using let and const. let allows reassignment, while const does not.
• Example of variable declaration: let country = 'Nigeria' assigns 'Nigeria' to country.
• Data types include strings (text), numbers (integer or float), boolean (true/false), undefined, object, and symbol.

Constants and Reassignment

• const variables require initialization upon declaration and cannot be reassigned. Example: const colour = 'red'.
• Attempting to reassign a const variable, like colour = 'yellow', will result in an error.

String Concatenation and Template Literals

• Strings can be concatenated using the + operator, e.g., console.log(country + ' has a population of ' + population + '.').

• Template literals using backticks (`) allow for multi-line strings and easy variable interpolation:

  • Example:

    console.log(`${country} is a country in ${continent} and has a population of ${population}.`);
    

Calculating Body Mass Index (BMI)

• BMI is calculated as mass divided by the square of height:
  • Example: const BMIJonas = massJonas / heightJonas ** 2;
• A comparison between two BMIs can be made using a boolean expression, e.g., const markHigherBMI = BMIMark > BMIJonas;.

Conditional Statements

• if statements are used for conditional execution of code, e.g., comparing BMIs to print which is higher.

• Basic structure:

  if (condition) {
      // code to execute if true
  } else {
      // code to execute if false
  }
  

Type Conversion and Coercion

• Type conversion changes a variable from one type to another explicitly using functions like Number().
• Type coercion automatically converts types during operations, e.g.:
  • Subtraction or multiplication of strings converts them to numbers: '23' - '10' equals 13.

Truthy and Falsy Values

• Falsy values: 0, undefined, null, NaN, '' (empty string).
• Truthy values: All other values are considered true, e.g., 100, 'Jonas', and {} (empty object) are truthy.

Switch Case Statements

• Use switch cases for multi-branch statements based on the value of a variable, e.g., checking the day of the week.
• Syntax includes defining cases followed by corresponding actions and a default case for unmatched values.

Ternary Operators

• Ternary operators provide a shorthand syntax for if-else statements:
  • Example: const allowed = ageDrink >= 18 ? 'wine' : 'water'; determines drink eligibility based on age.

Practical Input Handling

• The prompt-sync module allows synchronous user input in Node.js, making it easier to interactively gather user data.
• Example prompt: const ageDrink = prompt('How old are you?'); captures the user's age input.

Variables and Data Types

• Variables in JavaScript can be declared using let and const. let allows reassignment, while const does not.
• Example of variable declaration: let country = 'Nigeria' assigns 'Nigeria' to country.
• Data types include strings (text), numbers (integer or float), boolean (true/false), undefined, object, and symbol.

Constants and Reassignment

• const variables require initialization upon declaration and cannot be reassigned. Example: const colour = 'red'.
• Attempting to reassign a const variable, like colour = 'yellow', will result in an error.

String Concatenation and Template Literals

• Strings can be concatenated using the + operator, e.g., console.log(country + ' has a population of ' + population + '.').

• Template literals using backticks (`) allow for multi-line strings and easy variable interpolation:

  • Example:

    console.log(`${country} is a country in ${continent} and has a population of ${population}.`);
    

Calculating Body Mass Index (BMI)

• BMI is calculated as mass divided by the square of height:
  • Example: const BMIJonas = massJonas / heightJonas ** 2;
• A comparison between two BMIs can be made using a boolean expression, e.g., const markHigherBMI = BMIMark > BMIJonas;.

Conditional Statements

• if statements are used for conditional execution of code, e.g., comparing BMIs to print which is higher.

• Basic structure:

  if (condition) {
      // code to execute if true
  } else {
      // code to execute if false
  }
  

Type Conversion and Coercion

• Type conversion changes a variable from one type to another explicitly using functions like Number().
• Type coercion automatically converts types during operations, e.g.:
  • Subtraction or multiplication of strings converts them to numbers: '23' - '10' equals 13.

Truthy and Falsy Values

• Falsy values: 0, undefined, null, NaN, '' (empty string).
• Truthy values: All other values are considered true, e.g., 100, 'Jonas', and {} (empty object) are truthy.

Switch Case Statements

• Use switch cases for multi-branch statements based on the value of a variable, e.g., checking the day of the week.
• Syntax includes defining cases followed by corresponding actions and a default case for unmatched values.

Ternary Operators

• Ternary operators provide a shorthand syntax for if-else statements:
  • Example: const allowed = ageDrink >= 18 ? 'wine' : 'water'; determines drink eligibility based on age.

Practical Input Handling

• The prompt-sync module allows synchronous user input in Node.js, making it easier to interactively gather user data.
• Example prompt: const ageDrink = prompt('How old are you?'); captures the user's age input.

Variables and Data Types

• Variables in JavaScript can be declared using let for mutable variables and const for immutable ones.
• Example declaration: let country = 'Nigeria'; assigns 'Nigeria' to the variable country.
• JavaScript data types include:
  • Strings: Textual data
  • Numbers: Integers and floats
  • Booleans: True or false values
  • Undefined: Value not assigned
  • Objects: Collections of properties
  • Symbols: Unique identifiers

Constants and Reassignment

• const variables must be initialized during declaration and cannot be reassigned.
• Example: Trying to reassign const colour = 'red'; to colour = 'yellow'; results in an error.

String Concatenation and Template Literals

• Strings can be concatenated using the + operator.
  • Example: console.log(country + ' has a population of ' + population + '.');
• Template literals, enclosed in backticks (``), allow for multi-line strings and interpolation of variables.
  • Example: console.log(countryisacountryin{country} is a country in countryisacountryin{continent} and has a population of ${population}.);

Calculating Body Mass Index (BMI)

• BMI is calculated using the formula: mass divided by the square of height.
  • Example: const BMIJonas = massJonas / heightJonas ** 2;
• BMI comparisons can be made using boolean expressions.
  • Example: const markHigherBMI = BMIMark > BMIJonas;

Conditional Statements

• if statements facilitate conditional code execution.

• Basic structure:

  if (condition) {
      // code to execute if true
  } else {
      // code to execute if false
  }
  

Type Conversion and Coercion

• Type conversion: Explicitly change a variable's type using functions such as Number().
• Type coercion: Automatic conversion that occurs during operations, for example:
  • '23' - '10' results in 13, as strings convert to numbers during subtraction.

Truthy and Falsy Values

• Falsy values include: 0, undefined, null, NaN, and '' (empty string).
• Truthy values encompass all other values, including 100, 'Jonas', and {} (empty object).

Switch Case Statements

• Use switch statements for multiple branching based on a variable's value.
• Syntax includes defining cases and a default case for unhandled values.

Ternary Operators

• Ternary operators offer a shorthand for if-else statements.
  • Example: const allowed = ageDrink >= 18 ? 'wine' : 'water'; determines drink eligibility based on age.

Practical Input Handling

• prompt-sync module allows synchronous user input in Node.js for easy data collection.
  • Example: const ageDrink = prompt('How old are you?'); captures the user's age input.

Practical Input Handling

• The prompt-sync module enables synchronous user input in Node.js for interactive applications.
• Example usage: const ageDrink = prompt('How old are you?'); captures the user's age.

Variables and Data Types

• JavaScript allows variable declaration using let (reassignable) and const (non-reassignable).
• Example declaration: let country = 'Nigeria';.
• JavaScript supports various data types, including:
  • Strings (text)
  • Numbers (integers and floats)
  • Booleans (true/false)
  • Undefined
  • Objects
  • Symbols

Constants and Reassignment

• const variables must be initialized during declaration and cannot be reassigned.
• Attempting to reassign a const variable leads to an error; for example, const colour = 'red'; cannot be changed with colour = 'yellow';.

String Concatenation and Template Literals

• Strings can be combined using the + operator. For example: console.log(country + ' has a population of ' + population + '.');
• Template literals, enclosed in backticks (``), allow multi-line strings and easier variable interpolation, e.g.,:
  • console.log(${country} is a country in ${continent} and has a population of ${population}.);

Calculating Body Mass Index (BMI)

• BMI is computed as mass divided by the square of height, expressed as:
  • const BMIJonas = massJonas / heightJonas ** 2;
• Comparisons can be made using boolean expressions, e.g., const markHigherBMI = BMIMark > BMIJonas;.

Conditional Statements

• if statements facilitate conditional code execution. Basic structure:

  if (condition) {
      // code to execute if true
  } else {
      // code to execute if false
  }
  

Type Conversion and Coercion

• Type conversion is an explicit change of a variable's type using functions like Number().
• Type coercion occurs automatically during operations, for instance:
  • Subtracting or multiplying strings converts them to numbers ('23' - '10' results in 13).

Truthy and Falsy Values

• Falsy values in JavaScript: 0, undefined, null, NaN, and '' (empty string).
• Truthy values include everything else, such as 100, 'Jonas', and {} (empty object).

Switch Case Statements

• A switch statement provides a multi-branch selection based on a variable's value.
• Syntax includes defining cases with corresponding actions and a default for unmatched values.

Ternary Operators

• Ternary operators offer a shorthand for if-else statements.
• Example: const allowed = ageDrink >= 18 ? 'wine' : 'water'; determines drink eligibility based on age.

Example Code Snippets

• Comparing BMIs:

  if (BMIMark > BMIJonas) {
      console.log(`Mark's BMI ${BMIMark} is higher than John's!`);
  } else {
      console.log(`John's BMI ${BMIJonas} is higher than Mark's!`);
  }
  

• Demonstrating type conversion:

  const year = '1999';
  console.log(typeof(Number(year))); // converts string to number
  

Conclusion

• JavaScript features a robust structure for handling variables, data types, input, and conditional logic, enhancing programmability while ensuring efficient data manipulation.### Variable Declaration and Data Types
• let allows reassignment of variables, while const does not.
• Example: let country = 'Nigeria' assigns 'Nigeria' to the variable country.
• JavaScript supports multiple data types including strings, numbers (integers or floats), booleans (true/false), undefined, objects, and symbols.

Constants and Reassignment

• const variables must be initialized upon declaration and cannot be reassigned later.
• Example: const colour = 'red' cannot be changed to colour = 'yellow', which would throw an error.

String Concatenation and Template Literals

• Strings can be combined using the + operator, e.g., console.log(country + ' has a population of ' + population + '.').
• Template literals use backticks (`) for multi-line strings and facilitate easy variable interpolation:
  • Example: console.log(${country} is a country in ${continent} and has a population of ${population}.).

Body Mass Index (BMI) Calculation

• BMI is computed as mass divided by the square of height:
  • Example: const BMIJonas = massJonas / (heightJonas ** 2).
• Compare BMIs using a boolean expression, e.g., const markHigherBMI = BMIMark > BMIJonas.

Conditional Statements

• if statements execute code based on conditions. Basic structure:

  if (condition) {
      // code to execute if true
  } else {
      // code to execute if false
  }
  

Type Conversion and Coercion

• Type conversion explicitly changes variable types using functions like Number().
• Type coercion automatically converts types during operations, e.g., subtracting strings: '23' - '10' results in 13.

Truthy and Falsy Values

• Falsy values include: 0, undefined, null, NaN, and empty strings ('').
• Truthy values encompass all others, e.g., 100, 'Jonas', and empty objects ({}) are considered true.

Switch Case Statements

• switch statements handle multi-branch conditions based on variable values, such as checking the day of the week.
• Syntax involves defining cases followed by actions and a default case for unmatched values.

Ternary Operators

• Ternary operators act as shorthand for if-else statements.
• Example: const allowed = ageDrink >= 18 ? 'wine' : 'water' determines drink eligibility based on age.

Practical Input Handling

• The prompt-sync module enables synchronous user input in Node.js for interactive data collection.
• Example: const ageDrink = prompt('How old are you?') captures the user's age input.
• User input can be processed by converting it to a specific format, e.g., const day = prompt('Give in a day: ').toLowerCase().