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In this JavaScript tutorial, We will go through various examples and see the use of array.filter() method in action.
Usage: Array.filter() JavaScript Method
The filter method creates a new array containing all the elements which pass(evaluates to true) the test condition provided in the function.
Note: If no value evaluates to true condition then an empty array is created.
Syntax of Array.filter
JavaScript array.filter syntax is as below-
// arrow function
filter((element) => { ... })
filter((element,index) => { ... })
filter((element,index,array) => { ... })
// Callback function
filter(callbackFn)
filter(callbackFn, thisArg)
// Inline callback function
filter(function callbackFn(element) { ... })
filter(function callbackFn(element, index) { ... })
filter(function callbackFn(element, index, array){ ... })
filter(function callbackFn(element, index, array) { ... }, thisArg)
Example 1: Filter a Number Array
Task description -Filter the positive and negative numbers in Javascript using the Array.filter method.
//given array conating both positive & negative numbers
const numbers = [1,-5,2,0,-1,8,-3,10,9,-8];
//get the positive numbers in a new array
const positiveNum = numbers.filter(num => num > 0);
console.log(positiveNum); // show them on console
//get the negative numbers in a new array
const negativeNum = numbers.filter(num => num < 0);
console.log(negativeNum); // show them on console
Example 2: Filter a String Array
Task description- Get all the consonants from an array of alphabets. Use JavaScript Array.filter to complete the task.
//alphabet array
const alphabets = ['a','b','c','d','e','f','g','h','i','j',
'k','l','m','n','o','p','q','r','s','t',
'u','v','w','x','y','z'];
//get the consonents
const conconents = alphabets.filter(alpha =>
alpha!='a' && alpha!='e' &&
alpha!='i' && alpha!='o' &&
alpha!='u');
//show them on console
console.log(conconents);
Example 3: Filter an Array of Objects
Task description- Get the detail of the person who can vote, the voting criteria age should be equal to 18 or greater.
//array of objects containg the detail of people
const people= [
{ id: 1, name: "Jack", age: 18 },
{
id: 2,
name: "Jessy",
age: 20,
},
{
id: 3,
name: "Mark",
age: 16,
},
{
id: 4,
name: "Vishal",
age: 22,
}
];
//get the array with only who is eligable to vote using JS filter method
const pplCanVote = people.filter((people, index, arr) => {
return arr[index].age >= 18;
});
//show it on console.
console.log(pplCanVote);
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