7. How to find duplicate elements from an Array
//var myArr = [ 'x','y','a','x','b','b','a','c','b','k','b' ]; var myArr = [ 6, 4, 5, 5, 5, 2, 1, 3, 1, 1, 2, 1, 3, 4, 7 ]; // you must need to sort the array first var myArrSorted = myArr.sort(); // in filter function // 1st parameter is each element from an array // 2nd parameter is index of each element // 3rd parameters is an array itself // so we need to check if each element with its next element and // return only if element is not duplicate var result = myArrSorted.filter( function(element,index,arrayitself){ if(element !== arrayitself[index+1]){ return element; } }); console.log(result);