Javascript count duplicates and uniques and add to array

Question

I\'m trying to count duplicates in an array of dates and add them to a new array.

But i\'m only getting the duplicates and the amount of times they exist in the array. <

Answer 1

You might need an object for this, not an array. So what you are doing is already great, but the if condition is messing up:

$scope.result = {};
for (var i = 0; i < $scope.loginArray.length; ++i) {
  if (!$scope.result[$scope.loginArray[i]])
    $scope.result[$scope.loginArray[i]] = 0;
  ++$scope.result[$scope.loginArray[i]];
}

Snippet

var a = ['a', 'a', 'b', 'c', 'c'];
var r = {};
for (var i = 0; i < a.length; ++i) {
  if (!r[a[i]])
    r[a[i]] = 0;
  ++r[a[i]];
}
console.log(r);

Or in better way, you can use .reduce like how others have given. A simple reduce function will be:

var a = ['a', 'a', 'b', 'c', 'c'];
var r = a.reduce(function(c, e) {
  c[e] = (c[e] || 0) + 1;
  return c;
}, {});

console.log(r);