eclipse: проверить xml с xsd

//find duplicates:
//sort, then reduce - concat values equal previous element, skip others

//input
var a = [1, 2, 3, 1, 2, 1, 2]

//short version:
var duplicates = a.sort().reduce((d, v, i, a) => i && v === a[i - 1] ? d.concat(v) : d, [])
console.log(duplicates); //[1, 1, 2, 2]

//readable version:
var duplicates = a.sort().reduce((output, element, index, input) => {
  if ((index > 0) && (element === input[index - 1]))
    return output.concat(element)
  return output
}, [])
console.log(duplicates); //[1, 1, 2, 2]