JSFiddle - React, Tailwind, and code Playground

by ndw5015

JavaScript

function findDupe(data){
	let result = [];
  
  data.forEach(function(element, index){
  	if(data.indexOf(element, index +1) > -1){
    document.write(data.indexOf(element) + 'index of element' + '<br>');
    document.write(index + 'index' +'<br>');
    	if(result.indexOf(element) === -1){
      	result.push(element);
        //document.write(result);
      }
    }
    
  });
  return result;
}


findDupe([1,3,3,4,4,5]);