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8,611 Pointswhy can we use .map() in the first example?
i understand the logic of reduce and and map, but it's blurry to me when should i use each of these methods. thanks
1 Answer
Brendan Whiting
Front End Web Development Techdegree Graduate 84,738 PointsWe use map
when we have a list and we want to produce another list with some modification of each element.
const letters = ['a', 'b', 'c'];
const upperCaseLetters = letters.map(letter => letter.toUpperCase()); // [ 'A', 'B', 'C' ]
We use reduce
when we have a list and we want to distill it into one object according to some logic.
const lettersSmushedTogether = letters.reduce((acc, curr) => {
return acc + curr;
}, "") // "abc"
The confusing thing in the example in the video is that the object he's reducing the array into is... an array. But he took a two-dimensional array (an array of arrays) and distilled it down into a one-dimensional array.
const twoDimensionalLetters = [
['a', 'b', 'c'],
['d', 'e', 'f'],
['g', 'h', 'i']
];
const oneDimensionalLetters = twoDimensionalLetters.reduce((acc, curr) => {
return [...acc, ...curr];
}, []) // [ 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i' ]
I used the spread operator just as in the video.