Map, Reduce and filter function in Javascript Language

Map Function

It returns new array after some modifications iterate over each element.

Example: If you want to Multiply by 2 to every element in array, in simple approach it will look like this

const arr =[1,2,3,4,5]

const newArr =[]

for(let i=0; i<=arr.length-1; i++){

  newArr.push(arr[i]*2);

}

console.log(newArr)

And you will get output // 2,4,6,8,10

Same thing using map function you will do it like

const arr = [1,2,3,4,5]

console.log(arr.map(e => e*2))

And you will get same output // 2,4,6,8,10

Reduce Function

This function reduces an array of values down to just one value. To get the output value, it runs a reducer function on each element of the array.

example

const numbers = [1, 2, 3, 4]; 

const sum = numbers.reduce(function (result, item) {

 return result + item; 

}, 0);

console.log(sum);

Filter Function

The filter() method takes each element in an array and it applies a conditional statement against it. If this conditional returns true, the element gets pushed to the output array. If the condition returns false, the element does not get pushed to the output array.

Example

const numbers = [1, 2, 3, 4];

const evens = numbers.filter(item => item % 2 === 0);

console.log(evens); // [2, 4]