June 14, 2022

How to Get All Unique Values from Array in Javascript

By Krishnaa JavaScript Questions 0 Comments

In this tutorial, you will learn how to get all unique values from array in javascript. Arrays are a typical way to represent a collection of related elements. The data types of the items may or may not be identical. From a developer’s point of view, it can be a bit tricky to get all unique values from array.

This tutorial is mostly concerned with the string type. The toLowerCase() and toUpperCase() functions are only available for strings and cannot be used with numbers. Because there is no built-in technique to remove duplicate entries from an array, we must create a custom method to achieve our goal.

In the following example, we have a global array of fruits. Initially, we will display all fruit names on the screen. Upon click of a button, we will get all unique values from array and update our list. Please have a look over the code example and the steps given below.

HTML & CSS

We have 2 elements in the HTML file (button and ul).
The innerText for the button element is “Remove Duplicates”.
The ul element is empty as of now and we will populate it dynamically using javascript.
We have also included our javascript file script.js with a script tag at the bottom.

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta http-equiv="X-UA-Compatible" content="ie=edge">
  <title>Document</title>
</head>
<body>
  
  <button>Remove Duplicates</button>
  <ul></ul>
  <script src="script.js"></script>
</body>
</html>

Javascript

We have a global variable fruits and it holds an array of strings.
We have the addFruits() method which will populate our ul element with list of fruit names.
In addFruits() method, we are simply looping through the fruits array and creating a template string with a bunch of li elements.
We are displaying that list in the ul element by using the innerHTML property.
We are calling the addFruits() method to display our initial fruits list.
We have selected the button element using the document.querySelector() method and attached the click event listener to it.

Case Sensitive Comparison

We are using the Set constructor to create a Set of fruits. By default, you cannot have duplicate items in a Set. We are storing our fruits Set in the mySet variable
We are using Array.from() method to convert Set into an array. We are assigning it back to the fruits variable.
We are calling the addFruits() method to update our fruits list.

Case Insensitive Comparison

We are using the map() method to loop through all items in the array. Inside the loop, we are using the toLowerCase() method to have all fruit names in the lowercase.
We are using the filter() method to remove duplicate items from the array. Inside the loop, we are simply using the indexOf() method to check if a certain item is already present or not.
We are again using the map() method to capitalize the first letter of each fruit name.
Inside the loop, we are using the index of 0 to get the first letter and then using the toUpperCase() method to capitalize it. We are using the slice() method to slice the string from index 1. We are joining the capitalized letter and sliced string by using the addition (+) operator.
We are calling the addFruits() method to update our fruits list.

let fruits = ['Grapes', 'Apple', 'Orange', 'Papaya', 'Plum', 'Orange', 'Apple'];

function addFruits(){
    let template = fruits.map(fruit => `<li>${fruit}</li>`).join('\n');
    document.querySelector('ul').innerHTML = template;
}

addFruits();

document.querySelector('button').addEventListener('click', () =>{
    /* let mySet = new Set(fruits);
    fruits = Array.from(mySet);
    addFruits(); */

    fruits = fruits.map(fruit => fruit.toLowerCase());
    fruits = fruits.filter((item, index) => fruits.indexOf(item) == index);
    fruits = fruits.map(fruit => fruit[0].toUpperCase() + fruit.slice(1));
    addFruits();
});

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