Map and Reduce Methods
Exploring the map and reduce methods of the array.
In this lesson, we’ll look at two unique array methods, map
and reduce
, that can make arrays even more convenient.
Introduction
The map
and reduce
methods are used to get a modified version of the array or a reduced value using callback functions. Let’s look at the two methods individually.
map
method
The map
method applies a function to each element of the array and creates a new array of the returned values. Now, we can look at its uses.
Syntax of map
method
The syntax of the map
method looks like this:
arr.map(<function>);
The map
method above will take, as an argument, a function invoked for each element in the array. The function that will be passed is given arguments by the map
method in the following order.
function callbackfn(value: any, index: number, array: any[])
Again, for each element the callbackfn
will be passed with the value of the element as the first argument, followed by the index of the element as the second argument, and lastly the array itself as the third argument. This callbackfn
function takes from 0 to 3 arguments. Finally, a new array with all the returned values from the callbackfn
function will be returned by the map
method.
Check out the following example.
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