checkDuplicates.js

let sortedArray = [0, 1, 1, 2, 4, 18, 23, 23, 28, 30, 30, 30];

let withoutDuplicates = [0, 1, 2, 4, 18, 23, 28, 30];


function checkDuplicates(array) {
  var newArray = [];
  for (var i = 0; i < array.length; i++) {
    if (array[i] !== array[i + 1]) {
      newArray.push(array[i]);
    }
  }
  return newArray;
}

console.log(checkDuplicates(sortedArray));