These all are super important and are often used while developing a project or website. map(), filter & reduce()
are higher order functions, i.e. functions which have another function inside them.
1. map()
A map function basically iterates and applies a given operation on each element.
arr=[1,2,4,3,5,6]
function checkEven(x){
return x%2==0;
}
const ans=arr.map(checkEven)
console.log(ans)
Here it basically returns where an element is even or not and modifies value of each element present.
2. filter()
This function takes an array and check a condition on each element and filters out false values.
arr=[1,2,4,3,5,6]
const ans=arr.filter(function checkEven(x){
return x%2==0;
})
console.log(ans)
Here all the false values are removed. These functions do not reflect changes in the main array, arr
.
3. reduce()
boils down the output of an operation over the whole array to a single answer.
It takes an accumulator
that keeps track of ans at every step and a current
element. Here our ans
is the accumulator and x
is the current element of the array.
The },0)
part, this zero is the initial value of the accumulator ans
.
arr=[2,4,6,6,8,9,22]
const ans=arr.reduce(function checkMax(ans, x){
ans=ans>x?ans:x
return ans;
},0)
console.log(ans)
Here we keep track of maximum element and compare it with current to update it if bigger than max.
You can even pass arrow functions inside these functions. ⭐ MDN -Arrow functions
Top comments (3)
good post!
and just in case you didn't know, you can add the language in the code block, to add syntax highlight :) just add the language name after the opening backticks like
That was helpful, thank you so much!
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