打印javascript数组中的重复数

function printDuplicates(arr) {
  var countMap = new Map();
  var duplicates = [];

  for (var i = 0; i < arr.length; i++) {
    var element = arr[i];
    if (countMap.has(element)) {
      countMap.set(element, countMap.get(element) + 1);
    } else {
      countMap.set(element, 1);
    }
  }

  countMap.forEach(function (count, element) {
    if (count > 1) {
      duplicates.push(element);
    }
  });

  console.log("重复数: " + duplicates);
}

var array = [1, 2, 3, 4, 4, 5, 6, 6, 7];
printDuplicates(array);