Map, Filter, Reduce in Javascript


 .map(), .filter(), .reduce() are all array methods in javascript. Each method will iterate over an array and perform transformations or computation. Each will return a new array based on the result of the function. Lets see how to use each of these methods in this article.

Map :

The map() is a method that transforms an array according to the applied function and returns the updated output. It works on each element of an array. 

Syntax :[,object])

Example 1 

Double each elements in an array.: 

Example 2:

Binary of each element in an array:


The filter() method takes each element in an array and it applies a conditional statement against it. If the conditional returns true, it will get pushed into an output array , else it will not.

Example 1:

Find odd numbers in an array.

Example 2:

Numbers greater than 4 in array

The syntax of filter() is similar to map(), except the callback function should return true to keep the element or not 


The reduce() method reduces an array of values down to just one value. It runs a reducer function on each element of the array to get the output value.

Example 1:

Sum of the array:

Example 2:

Find maximum number in an array


We can try to replace some of our for loops with .map(), .filter(), .reduce() where it seems to fit. The code will become much easier to read.

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