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Map And Filter Javascript Difference

Written by Ben Javu Apr 06, 2023 · 4 min read
Map And Filter Javascript Difference

Table of Contents

HigherOrder Functions
HigherOrder Functions from www.modernescpp.com

Introduction

JavaScript is a highly popular programming language in web development. It provides a rich set of functionalities for developers to create interactive and dynamic web pages. Two of the most commonly used functions in JavaScript are map() and filter(). Both functions are used to manipulate arrays, but they have different purposes and functionalities.

What is the map() function?

The map() function is used to iterate over an array and return a new array with modified values. It takes a function as an argument that is executed for each element in the array. The returned value of the function is added to the new array. The syntax of the map() function is as follows: ``` array.map(function(currentValue, index, arr), thisValue) ```

What is the filter() function?

The filter() function is used to iterate over an array and return a new array with elements that pass a certain condition. It takes a function as an argument that is executed for each element in the array. The returned value of the function is checked and if it is true, the element is added to the new array. The syntax of the filter() function is as follows: ``` array.filter(function(currentValue, index, arr), thisValue) ```

Map() vs Filter()

While both map() and filter() functions are used to manipulate arrays, they have different purposes and functionalities. Map() function is used to iterate over an array and modify each element in the array. It returns a new array with the modified elements. For example, if we have an array of numbers and we want to double each number, we can use the map() function as follows: ``` const numbers = [2, 4, 6, 8]; const doubledNumbers = numbers.map(num => num * 2); ``` The output of the above code will be a new array with doubled values [4, 8, 12, 16]. On the other hand, the filter() function is used to iterate over an array and return a new array with only the elements that pass a certain condition. For example, if we have an array of numbers and we want to filter out the even numbers, we can use the filter() function as follows: ``` const numbers = [1, 2, 3, 4, 5, 6]; const oddNumbers = numbers.filter(num => num % 2 !== 0); ``` The output of the above code will be a new array with only the odd numbers [1, 3, 5].

Question and Answer

Q: Can we use map() and filter() function together?

Yes, we can use map() and filter() function together. For example, if we have an array of objects and we want to filter out the objects that have a certain property value, and then modify the remaining objects, we can use map() and filter() functions together as follows: ``` const products = [ {id: 1, name: 'Product 1', price: 10}, {id: 2, name: 'Product 2', price: 20}, {id: 3, name: 'Product 3', price: 30}, {id: 4, name: 'Product 4', price: 40}, ]; const filteredProducts = products.filter(product => product.price > 20); const modifiedProducts = filteredProducts.map(product => ({...product, price: product.price * 2})); ``` The output of the above code will be a new array with modified objects that have a price greater than 20.

Q: Which function is better to use, map() or filter()?

It depends on the requirement. If we want to modify each element in an array, we can use map() function. If we want to filter out the elements based on a certain condition, we can use filter() function. Both functions are very useful and have their own advantages. It's up to the developer to decide which function to use based on the requirement.

Conclusion

In this article, we learned about the map() and filter() functions in JavaScript. We saw the syntax and functionalities of both functions. We also saw the difference between the two functions and learned when to use which function. Both functions are very useful and can be used together to achieve the desired output.
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