JSFiddle - React, Tailwind, and code Playground

by _sir

HTML

<h3>Take an array and return the number of unique duplicates in it</h3>

<p>
<strong>Your answer should be: </strong>0, 1, 2
</p>
<div id="output"></div>

JavaScript

var arr = [[1, 2, 3],[1, 1, 2, 3],[1, 2, 2, 3, 3, 3]];

const countInArray = (value, array) => {
	return array.filter(arrValue=>(arrValue === value)).length;
}

let output = [];
arr.map((array)=>{
	let count = 0;
	array.map(value=>{
    const countsInArray = countInArray(value, array);
    if(countsInArray > 1){
    	count = count+1;
    }
    array = array.filter(arrValue=>arrValue !== value);
  })
  console.log("value", count);
  output.push(count);
});

let outputText = '';
output.map(value=>{
	outputText = outputText + ', ' + value
});

document.getElementById("output").innerHTML = outputText.substr(1, outputText.length);