Implement filter in javascript
Predicating Arrays
Filtering also key method for manipulating collections. We iterate over the array and add an item to the new array if it passes the test.
- We will be solving a problem using
Array.prototype.forEach()
. - We will define
Array.prototype.filter()
usingArray.prototype.forEach()
. - We will solve the same problem using
Array.prototype.filter()
This post is a follow up post of the
- Getting started Functional Programming in JavaScript. I would recommend reading that post first.
Problem
Filter only those videos with a rating of 5.0
Let's solve with
Array.prototype.forEach()
Do notice that the array projections have two operations in common:
- Traversing the source array
- If an item passes the test then add an item to collection
We can abstract these common operations in Array.prototype.filter()
Implement
Array.prototype.filter()
usingArray.prototype.forEach()
Lets solve with
Array.prtotype.filter()
Key Learnings
- Predicate methods iterates over array and creates a new array of elements which passes the test
Array.prototype.filter()
allows you to specify the test