remove-duplicates-from-sorted-array

//Given a sorted array, remove the duplicates in-place such that each element appear only once and return the new length.
//Do not allocate extra space for another array, you must do this by modifying the input array in-place with O(1) extra memory.

//Example: Given nums = [1,1,2], Your function should return length = 2, with the first two elements of nums
//being 1 and 2 respectively. It doesn't matter what you leave beyond the new length.

console.log('OutPut:', removeDuplicates([1,1,2]), 'Expected: 2')
console.log('OutPut:', removeDuplicates([1,1,1]), 'Expected: 1')
console.log('OutPut:', removeDuplicates([1,2,2,7,8,8,8,9,12,16,16,118]), 'Expected: 8')

function removeDuplicates(nums) {
    var lastNumInArray;
    var deleteIndexArray = [];
    nums.forEach(function(num,index) {
        if (lastNumInArray === num) {
            deleteIndexArray.push(index);
        } else {
            lastNumInArray = num;
        }
    });
    deleteIndexArray.reverse().forEach(function(arrayIndex) {
        nums.splice(arrayIndex, 1);
    });
    return nums.length;
}