logic for solving problem 8 in js added to main

main.js

@@ -254,4 +254,34 @@ function problem7() {
 var btn8 = document.getElementById("btn8");
 btn8.onclick = function () {
 	document.getElementById("answer8").innerHTML = problem8();
+}
+// PROBLEM 8: FUNCTION
+function problem8() {
+	const digits = '7316717653133062491922511967442657474235534919493496983520312774506326239578318016984801869478851843858615607891129494954595017379583319528532088055111254069874715852386305071569329096329522744304355766896648950445244523161731856403098711121722383113622298934233803081353362766142828064444866452387493035890729629049156044077239071381051585930796086670172427121883998797908792274921901699720888093776657273330010533678812202354218097512545405947522435258490771167055601360483958644670632441572215539753697817977846174064955149290862569321978468622482839722413756570560574902614079729686524145351004748216637048440319989000889524345065854122758866688116427171479924442928230863465674813919123162824586178664583591245665294765456828489128831426076900422421902267105562632111110937054421750694165896040807198403850962455444362981230987879927244284909188845801561660979191338754992005240636899125607176060588611646710940507754100225698315520005593572972571636269561882670428252483600823257530420752963450';
+
+	var num = document.getElementById('input8').value;
+
+	let currentIndex = 0;
+	let lastIndex = digits.length - 1 - num;
+
+	let currentProduct = 0;
+	let largestProduct = 0;
+
+	while (currentIndex < lastIndex) {
+		currentProduct = findCurrentProduct(currentIndex);
+
+		if (currentProduct > largestProduct) {
+			largestProduct = currentProduct;
+		}
+		currentIndex++;
+	}
+	return largestProduct;
+
+	function findCurrentProduct(currentIndex) {
+		let currentProduct = 1;
+		for (var i = 0; i < num; i++) {
+			currentProduct *= Number(digits[currentIndex + i]);
+		}
+		return currentProduct;
+	}
 }