JavaScript Callbacks and Arrays Quiz

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Questions and Answers

What is the primary purpose of a callback function?

To access elements in an array

To execute code in response to an event (correct)

To store values of mixed types

To dynamically create JavaScript arrays

Which of the following methods adds an element to the end of a JavaScript array?

insert()

push() (correct)

unshift()

append()

How can you access the length of a JavaScript array?

Using the length() function

Using the count() function

Using the length property (correct)

Using the getSize() method

Which of the following correctly creates a JavaScript array using array literal notation?

let arrayName = [1, 2, 3]; Signup and view all the answers

What will be the output of the following code? let seas = ['A', 'B']; seas.push('C'); console.log(seas);

['A', 'B', 'C'] Signup and view all the answers

What is a characteristic of a JavaScript array?

It can hold values of mixed types Signup and view all the answers

Which method would you use to add an element at the beginning of an array?

unshift() Signup and view all the answers

Which statement accurately reflects how to create an array using the Array constructor?

let scores = new Array(9, 10); Signup and view all the answers

What is the result of using the pop() method on the array ['Black Sea', 'Caribbean Sea', 'North Sea', 'Baltic Sea']?

Baltic Sea Signup and view all the answers

What does the shift() method do to an array?

Removes the first element. Signup and view all the answers

Which statement correctly describes the use of the forEach() method?

forEach() executes a function once for each array element. Signup and view all the answers

In the context of forEach(), what does the currentValue parameter represent?

The value of the current element. Signup and view all the answers

What is the output of the following code? let students = ['John', 'Sara', 'Jack']; students.forEach(myFunction); function myFunction(item) { console.log(item); }

John Sara Jack Signup and view all the answers

What is the purpose of the map method in arrays?

To run every item through a function and return a new array. Signup and view all the answers

What will the students array contain after executing this code: let students = ['John', 'Sara', 'Jack']; students.forEach(myFunction); function myFunction(item, index, arr) { arr[index] = 'Hello ' + item; }?

['Hello John', 'Hello Sara', 'Hello Jack'] Signup and view all the answers

Which of the following is NOT a parameter of the forEach() method?

nextValue Signup and view all the answers

What does the map() method do in array manipulation?

It applies a function to each element and creates a new array with the results. Signup and view all the answers

What is the purpose of the filter() method?

To process each element and return an array of elements that meet specific criteria. Signup and view all the answers

In the reduce() method, what does the accumulator represent?

The initial value that the accumulator starts with. Signup and view all the answers

What will be the output of the following code snippet? let arr = [10, 20, 30]; console.log(arr.reduce((sum, i) => sum + i));

60 Signup and view all the answers

How is the callback function structured in the reduce() method?

It requires both an accumulator and a current element as parameters. Signup and view all the answers

If you use the following code, what will be the result of console.log(highTestScores); in the example provided? let highTestScores = testScores.filter(isHighScore);

[90, 100, 81] Signup and view all the answers

Which of the following statements about the map() and filter() methods is true?

Map creates a new array based on the return values of a function, while filter creates a new array based on a condition. Signup and view all the answers

Study Notes

Callback Functions

A callback function is a function passed as an argument to another function.
It's executed after the completion of some operations.
A callback's purpose is to execute code in response to an event.
Callbacks allow applications to perform actions in response to user events, such as key presses or mouse clicks.

JavaScript Arrays

JavaScript arrays can hold values of mixed types.
Array sizes are dynamic (not fixed).
Creating arrays: Use Array constructor (new Array(...)) or array literal notation ([element1, element2, ...]).
Accessing array elements: Use index in square brackets (array[index]).
Array length: Use .length property to get the number of elements.

Array Operations

push(): Adds an element to the end of an array.
unshift(): Adds an element to the beginning of an array.
pop(): Removes and returns the last element from the array.
shift(): Removes and returns the first element from the array.
forEach(): Executes a provided function once for each array element.
- The provided function receives the current element, index, and array as arguments.
map(): Creates a new array with the results of calling a provided function on every element in the original array.
filter(): Creates a new array with all elements that pass the test implemented by the provided function.
reduce(): Executes a reducer function (that you provide) on each element of the array, resulting in a single output value.
- The reducer function takes two arguments: accumulator and currentValue.
- Accumulator is the result of the previous calls to the reducer function.
- reduce() can optionally take an initial value as the 2nd argument.

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Description

Test your knowledge on JavaScript callbacks and array operations through this engaging quiz. Explore the concepts of passing functions as arguments and manipulating arrays with various methods. Familiarity with these topics is essential for any aspiring JavaScript developer.

JavaScript Callbacks and Arrays Quiz

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Podcast

Questions and Answers

What is the primary purpose of a callback function?

Which of the following methods adds an element to the end of a JavaScript array?

How can you access the length of a JavaScript array?

Which of the following correctly creates a JavaScript array using array literal notation?

What will be the output of the following code? let seas = ['A', 'B']; seas.push('C'); console.log(seas);

What is a characteristic of a JavaScript array?

Which method would you use to add an element at the beginning of an array?

Which statement accurately reflects how to create an array using the Array constructor?

What is the result of using the pop() method on the array ['Black Sea', 'Caribbean Sea', 'North Sea', 'Baltic Sea']?

What does the shift() method do to an array?

Which statement correctly describes the use of the forEach() method?

In the context of forEach(), what does the currentValue parameter represent?

What is the output of the following code? let students = ['John', 'Sara', 'Jack']; students.forEach(myFunction); function myFunction(item) { console.log(item); }

What is the purpose of the map method in arrays?

What will the students array contain after executing this code: let students = ['John', 'Sara', 'Jack']; students.forEach(myFunction); function myFunction(item, index, arr) { arr[index] = 'Hello ' + item; }?

Which of the following is NOT a parameter of the forEach() method?

What does the map() method do in array manipulation?

What is the purpose of the filter() method?

In the reduce() method, what does the accumulator represent?

What will be the output of the following code snippet? let arr = [10, 20, 30]; console.log(arr.reduce((sum, i) => sum + i));

How is the callback function structured in the reduce() method?

If you use the following code, what will be the result of console.log(highTestScores); in the example provided? let highTestScores = testScores.filter(isHighScore);

Which of the following statements about the map() and filter() methods is true?

Study Notes

Callback Functions

JavaScript Arrays

Array Operations

Studying That Suits You

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