Algorithm to remove duplicates from a sorted array

RemoveDuplicates.js

const removeDuplicates = (nums) =>{

	if( nums == undefined )
		return 0;
	if( nums.length == 0 )
		return 0;

	let pointerOne = 0;
	let pointerTwo = 1;
	let occurence = 0;
  
	while( pointerOne < nums.length ){

		if( nums[pointerOne] != nums[pointerTwo] ){

			occurence++;
			pointerOne = pointerTwo;
		}

		pointerTwo++;
	}
	return occurence;
}