Higher Order Functions in JavaScript

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Questions and Answers

In JavaScript, which array method is used to iterate over the elements of an array and apply a callback function to each element?

filter

forEach (correct)

reduce

map

If we want to create a new array with modified elements based on a specific condition from an existing array, which array method is most suitable?

forEach

find

filter

map (correct)

Which array method does NOT return a new array but is commonly used for performing side effects on each element without modifying the original array?

map

some

forEach (correct)

filter

If we want to filter out elements from an array based on a specified condition, which array method should be used?

filter Signup and view all the answers

Which of the following array methods is commonly used to transform each element of an array into a new value using an accumulator and a callback function?

map Signup and view all the answers

What is the purpose of the filter() function in JavaScript?

To create a new array with elements that pass a provided test function Signup and view all the answers

Which array method is used to apply a function to each element of an array without creating a new array?

forEach() Signup and view all the answers

In the context of the provided text, what is the filtering condition used in the examples given for the higher-order functions?

All elements greater than 10 Signup and view all the answers

Which higher-order function in JavaScript can be used to delay the execution of a specified function?

setTimeout() Signup and view all the answers

If you need to create a new array based on modifying each element of an existing array, which function among the ones mentioned is most appropriate?

map() Signup and view all the answers

Which array method is specifically designed to create a new array with elements that meet a certain condition?

filter() Signup and view all the answers

What does the map() function in JavaScript do?

Create a new array by applying a callback function to each element of an original array Signup and view all the answers

Which array method is best suited for transforming elements and building new data structures?

map Signup and view all the answers

In the context of array functions, what does the filter() function do?

Create a new array with elements that pass a test specified by a callback function Signup and view all the answers

How do you filter persons with a salary above 1300 and age over 26 using the filter function?

(person) => person.age > 26 && person.salary > 1300 Signup and view all the answers

Which of the following array methods iterates over each element of an array?

forEach Signup and view all the answers

What is the main difference between the map() and filter() functions in JavaScript?

map() is used for iteration, while filter() is used for conditional selection of elements Signup and view all the answers

Study Notes

Array Functions

Filter(): extracts specific elements from an array based on certain criteria, creating a new array with the elements that pass the test.
Callback function: function callback(element, index, array) { // Return value for new_array } with three parameters: element (current element in array), index (current index of element, optional), and array (original array, optional).

Filter Example

Filtering persons with salary above 1300 and age over 26:
- Using anonymous function: var newpersons = persons.filter(function(person){ if(person.salary > 1200 && person.age > 27) return person });
- Using arrow function: var newpersons = persons.filter( (person) => person.age > 27 && person.salary > 1200 );

Map Function

Creates a new array by applying a callback function to each element of an original array.
var new_array = arr.map(function callback(element, index, array) { // Return value for new_array });
Example: adding a 10% bonus to each person's salary.

Map and Filter Example

Printing a report with name and salary for all employees older than 25 years:
- Using map and filter functions.

ForEach Function

Iterates over the elements of an array, taking a callback function as an argument.
arr.foreach(function callback(element, index, array) { // iterate over element });
Does not return any value and does not modify the original array.
Commonly used for performing side effects on each element of an array.