JavaScript: Filter out the non-unique values in an array

JavaScript fundamental (ES6 Syntax): Exercise-22 with Solution

Filter Non-Unique Values in Array

Write a JavaScript program to filter out non-unique values in an array.

• Use new Set() and the spread operator (...) to create an array of the unique values in arr.
• Use Array.prototype.filter() to create an array containing only the unique values.

Sample Solution:

JavaScript Code:

//#Source https://bit.ly/2neWfJ2 
// Define a function called `filter_Non_Unique` that filters an array and returns only the elements that are not unique.
const filter_Non_Unique = arr => arr.filter(i => arr.indexOf(i) === arr.lastIndexOf(i));

// Example usage
console.log(filter_Non_Unique([1, 2, 2, 3, 4, 4, 5]));  
console.log(filter_Non_Unique([1, 2, 3, 4]));   

Output:

[1,3,5]
[1,2,3,4]

Visual Presentation:

Flowchart:

Live Demo:

See the Pen javascript-basic-exercise-1-22 by w3resource (@w3resource) on CodePen.

For more Practice: Solve these Related Problems:

• Write a JavaScript program that filters out duplicate values from an array, returning only the unique ones.
• Write a JavaScript function that uses a frequency counter to eliminate non-unique elements from an array.
• Write a JavaScript program that returns an array containing only elements that occur exactly once in the original array.

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