const arr1 = [1, 3, 5, 7, 11, 17, 21];
const arr2 = [-1, 0, 2, 3, 9, 11, 29];

function intersection(arr1, arr2) {

	let result = [];
	let p1 = 0, p2 = 0;

	while((p1 < arr1.length) && (p2 < arr2.length)) {
		if (arr1[p1] == arr2[p2]) {
			result.push(arr1[p1]);
			p1++;
			p2++;
		} else if (arr1[p1] < arr2[p2]) {
			p1++;
		} else {
			p2++;
		}
	}

	return result;
}

let try1 = intersection(arr1, arr2);
console.log(try1);