.filter()

So I am kicking myself I haven’t been using this earlier. It’s actually rather simple yet very useful. 🤦‍♂️

So like other methods for arrays, we can use the call back function (the function we pass to another function) in a couple of ways:

//ES5 syntax with function inline
array.filter(
	function(element) { //some set a rule here }
);

//ES6 Arrow function. again inline
array.filter(
	(record) => record.age > 10
 );

//as a call back function
function myRule(element) {
	//some set a rule here
}
array.filter(myRule);

So to see it in action we will use the same object we have used for the .find() post.

const array = [
  {
    id: 1,
    firstName: "John",
    lastName: "Doe",
    age: 50,
    eyeColor: "blue",
  },
  {
    id: 2,
    firstName: "Jane",
    lastName: "Doe",
    age: 40,
    eyeColor: "green",
  },
  {
    id: 3,
    firstName: "Dan",
    lastName: "Petersen",
    age: 200,
    eyeColor: "brown",
  },
];

Again, this is a simple Array of objects. Something like you’d see in a standard user table.

const filteredArray = array.filter((record) => record.age > 45);
console.log(filteredArray.length); //output: 2

Great! we can see a new Array has been created but is only 2 items in the array. 👏

You can use destructuring again:

const filteredArray2 = array.filter(({ age }) => age > 45);
console.log(filteredArray2.length); //output: 2

So as I continue with NodeJS and MySQL & APIs, these types of data manipulation methods will be very useful! 👌

Resources:

JS: Filter

.filter()