b) A shorter syntax for writing function expressions
c) A function that can only be used as a callback
d) A function that automatically binds to its parent object
Answer:
b) A shorter syntax for writing function expressions
Explanation:
Arrow functions provide a shorter syntax for writing function expressions in JavaScript. They allow for a more concise way to write functions.
2. How is an arrow function expressed in JavaScript?
a) (parameters) => { statements }
b) function(parameters) => { statements }
c) (parameters) = { statements }
d) => (parameters) { statements }
Answer:
a) (parameters) => { statements }
Explanation:
Arrow functions are defined using the arrow (=>) syntax, with parameters on the left side of the arrow and function statements on the right.
3. What is the main difference between arrow functions and traditional functions in terms of 'this'?
a) Arrow functions have their own 'this' context
b) Arrow functions do not have their own 'this' context
c) Arrow functions redefine 'this' within each block
d) There is no difference
Answer:
b) Arrow functions do not have their own 'this' context
Explanation:
Arrow functions do not have their own 'this' context; instead, 'this' refers to the surrounding lexical context.
4. Can arrow functions be used as constructors?
a) Yes, they can
b) No, they cannot
c) Only in strict mode
d) Only if they don't have parameters
Answer:
b) No, they cannot
Explanation:
Arrow functions cannot be used as constructors and will throw an error if used with the new keyword.
5. How does an arrow function return a single expression?
a) By explicitly using the return keyword
b) It automatically returns the expression
c) By using the return() method
d) By enclosing the expression in parentheses
Answer:
b) It automatically returns the expression
Explanation:
In an arrow function, if you have a single expression, it is returned automatically without the need for the return keyword.
6. What happens when you use parentheses around the body of an arrow function?
a) It's a syntax error
b) It indicates an implicit return
c) It's used for returning objects
d) It creates a function block
Answer:
b) It indicates an implicit return
Explanation:
Using parentheses around the body of an arrow function indicates an implicit return. This is commonly used for returning object literals.
7. Can arrow functions be named?
a) Yes, when they are assigned to a variable
b) No, they are always anonymous
c) Yes, by using the function keyword
d) Only if they are not assigned to a variable
Answer:
a) Yes, when they are assigned to a variable
Explanation:
Arrow functions are anonymous. However, they can be named indirectly by assigning them to variables.
8. How do you handle multiple parameters in an arrow function?
a) By separating them with a comma within parentheses
b) By using the spread operator
c) By creating multiple arrow functions
d) Multiple parameters are not allowed
Answer:
a) By separating them with a comma within parentheses
Explanation:
Multiple parameters in an arrow function are handled by separating them with a comma within parentheses.
9. What is a common use case for arrow functions in JavaScript?
a) As constructors for objects
b) For short callback functions
c) To redefine the value of 'this'
d) As methods in object literals
Answer:
b) For short callback functions
Explanation:
Arrow functions are commonly used for short callback functions due to their concise syntax.
10. How are arguments handled in an arrow function?
a) Using the arguments object
b) Arrow functions do not have arguments
c) By explicitly defining each argument
d) Using rest parameters
Answer:
d) Using rest parameters
Explanation:
Arrow functions do not have their own arguments object. However, you can handle arguments using rest parameters.
11. How does the arrow function treat the 'new.target' keyword?
a) It ignores it
b) It throws an error if used
c) It treats it the same as in regular functions
d) It always returns undefined
Answer:
b) It throws an error if used
Explanation:
Arrow functions do not have a new.target keyword; using it within an arrow function will throw an error.
12. Can arrow functions be used as methods in an object literal?
a) Yes, they can
b) No, they should not be used
c) Only if they don't use 'this'
d) Only in ES6 or later
Answer:
b) No, they should not be used
Explanation:
While you can use arrow functions as methods in object literals, it is not recommended because they inherit the 'this' value from the enclosing scope, which can lead to unexpected behavior.
13. What is the output of using 'this' inside an arrow function within a method?
a) The object that contains the method
b) The global object
c) The arrow function itself
d) The object that called the method
Answer:
b) The global object
Explanation:
When using 'this' inside an arrow function that is within a method, 'this' refers to the global object, as arrow functions do not have their own 'this'.
14. Can you create immediately invoked function expressions (IIFE) with arrow functions?
a) Yes
b) No
c) Only in non-strict mode
d) Only with a single expression
Answer:
a) Yes
Explanation:
Arrow functions can be used to create immediately invoked function expressions (IIFE) by enclosing the arrow function and its invocation in parentheses.
15. How do you specify a default parameter value in an arrow function?
a) Using the default keyword
b) It's not possible in arrow functions
c) By initializing the parameter in the function body
d) By assigning a value in the parameter list
Answer:
d) By assigning a value in the parameter list
Explanation:
Default parameter values in arrow functions are specified by assigning a value to the parameter in the function's parameter list.