1. What is the primary purpose of a function in JavaScript?
a) To iterate over arrays
b) To execute a block of code when invoked
c) To store data
d) To create HTML content
Answer:
b) To execute a block of code when invoked
Explanation:
A JavaScript function is a block of code designed to perform a particular task and is executed when it is invoked or called.
2. Which of the following is the correct syntax to define a function in JavaScript?
a) function = myFunction(p1, p2) {…}
b) function myFunction(p1, p2) {…}
c) myFunction(p1, p2) = function {…}
d) myFunction function(p1, p2) {…}
Answer:
b) function myFunction(p1, p2) {…}
Explanation:
A JavaScript function is defined with the function keyword, followed by a name and parentheses that may include parameter names.
3. How are arguments passed to a function in JavaScript?
a) Through global variables
b) As properties of an object
c) As values or variables within the function's parentheses
d) Via return statements from other functions
Answer:
c) As values or variables within the function's parentheses
Explanation:
Function arguments are the values received by the function when it is invoked, and they are passed within the parentheses of the function call.
4. What is the result of a JavaScript function when the return statement is executed?
a) The function pauses execution
b) The function continues to the next line of code
c) The function stops executing and returns a value
d) The function resets its parameters to their initial values
Answer:
c) The function stops executing and returns a value
Explanation:
When a return statement is reached, the function stops executing and returns the value specified by the return statement.
5. Which statement accurately describes JavaScript functions?
a) They can only be defined once and not reused
b) They are executed immediately upon definition
c) They allow code to be reused with different arguments
d) They cannot return values
Answer:
c) They allow code to be reused with different arguments
Explanation:
Functions enable code reuse and can be executed multiple times with different arguments to produce different results.
6. What does the () operator do when used with a function name?
a) Defines the function
b) Deletes the function
c) Invokes or calls the function
d) Assigns a value to the function
Answer:
c) Invokes or calls the function
Explanation:
The () operator is used to invoke or call a function in JavaScript.
7. In JavaScript, what are function expressions?
a) Variables that store data
b) Statements that declare functions
c) Functions assigned to variables
d) Syntax errors
Answer:
c) Functions assigned to variables
Explanation:
Function expressions involve defining a function and assigning it to a variable. These functions can be anonymous and are invoked using the variable name.
8. What does the Function() constructor in JavaScript do?
a) Creates a new variable
b) Instantiates a new function object
c) Calls a function
d) Returns the length of a function
Answer:
b) Instantiates a new function object
Explanation:
The Function() constructor in JavaScript is used to create new function objects.
9. How does function hoisting affect function declarations in JavaScript?
a) Functions must be defined at the top of the script
b) Functions can be called before they are declared
c) Functions are automatically converted to expressions
d) Functions are executed immediately
Answer:
b) Functions can be called before they are declared
Explanation:
Due to function hoisting, function declarations in JavaScript can be called before they are declared in the code.
10. What is a self-invoking function in JavaScript?
a) A function that calls itself recursively
b) A function that is automatically invoked after it is defined
c) A function that can only be invoked once
d) A function that must be manually invoked
Answer:
b) A function that is automatically invoked after it is defined
Explanation:
Self-invoking functions are function expressions that automatically execute immediately after they are defined.
11. Can JavaScript functions be used as values in expressions?
a) No, functions cannot be used in expressions
b) Yes, but only if they don't return a value
c) Yes, functions can be used as values in expressions
d) No, functions can only be used as standalone entities
Answer:
c) Yes, functions can be used as values in expressions
Explanation:
JavaScript functions can be used as values and can be part of expressions, just like any other value.
12. What is a unique feature of arrow functions in JavaScript?
a) They can return multiple values at once
b) They do not have their own this context
c) They are hoisted like traditional function declarations
d) They cannot have parameters
Answer:
b) They do not have their own this context
Explanation:
Arrow functions do not have their own this context, which makes them behave differently than traditional functions, especially in object methods.
13. What happens when you access a function without the () in JavaScript?
a) The function is deleted
b) The function is invoked
c) The function's code as a string is returned
d) The function object is returned
Answer:
d) The function object is returned
Explanation:
Accessing a function without () returns the function object itself, not the result of the function.
14. What is a characteristic of local variables in JavaScript functions?
a) They can be accessed anywhere in the script
b) They are shared across all functions
c) They can only be accessed within the function where they are declared
d) They persist after the function execution is completed
Answer:
c) They can only be accessed within the function where they are declared
Explanation:
Local variables in JavaScript functions are confined to the scope of the function in which they are declared and cannot be accessed outside of it.
15. How are arrow functions written differently from traditional functions in JavaScript?
a) They use the var keyword
b) They require the function keyword
c) They omit the function and return keywords and curly brackets for single statements
d) They must always return an object
Answer:
c) They omit the function and return keywords and curly brackets for single statements
Explanation:
Arrow functions allow a shorter syntax and do not require the function keyword, the return keyword, and curly brackets for single statements.
16. What is the behavior of arguments.length in a JavaScript function?
a) It sets the number of parameters the function accepts
b) It returns the number of arguments passed to the function
c) It determines the maximum number of arguments allowed
d) It always returns the value zero
Answer:
b) It returns the number of arguments passed to the function
Explanation:
The arguments.length property in a JavaScript function returns the number of arguments that were passed to the function when it was invoked.
17. What is the difference between function declarations and function expressions in terms of hoisting?
a) Both are hoisted to the top of their scope
b) Function declarations are hoisted, but function expressions are not
c) Function expressions are hoisted, but function declarations are not
d) Neither function declarations nor expressions are hoisted
Answer:
b) Function declarations are hoisted, but function expressions are not
Explanation:
Function declarations are hoisted, meaning they can be called before they are defined in the code. Function expressions are not hoisted in the same way.
18. Which statement is true about functions defined using the Function() constructor?
a) They are the preferred way to define functions in JavaScript
b) They are identical to function expressions
c) They are rarely used and can be avoided
d) They automatically execute upon definition
Answer:
c) They are rarely used and can be avoided
Explanation:
While it's possible to define functions using the Function() constructor, this method is less common and often can be avoided in favor of other function definitions.
19. How does the use of const with arrow functions benefit the code?
a) It allows the function to be reassigned
b) It ensures the function cannot be hoisted
c) It prevents the function from being redeclared or reassigned
d) It increases the execution speed of the function
Answer:
c) It prevents the function from being redeclared or reassigned
Explanation:
Using const with arrow functions (or any function expression) ensures that the function cannot be redeclared or reassigned, which helps maintain code stability.
20. In what scenario is an arrow function not suitable in JavaScript?
a) As a method inside an object
b) For simple arithmetic operations
c) When a concise syntax is required
d) When used as a callback function
Answer:
a) As a method inside an object
Explanation:
Arrow functions are not well suited for defining object methods because they do not have their own this context, which is often needed in object methods.