2016 Update

Task/Sum-multiples-of-3-and-5/JavaScript/sum-multiples-of-3-and-5-4.js

@@ -0,0 +1,5 @@
+function sm35(n){
+	var s=0, inc=[3,2,1,3,1,2,3]
+	for (var j=6, i=0; i<n; j+=j==6?-j:1, i+=inc[j]) s+=i
+	return s
+}

Task/Sum-multiples-of-3-and-5/JavaScript/sum-multiples-of-3-and-5-5.js

@@ -0,0 +1,7 @@
+function sm35(n){
+	return tri(n,3) + tri(n,5) - tri(n,15)
+	function tri(n, f) {
+		n = Math.floor((n-1) / f)
+		return f * n * (n+1) / 2
+	}
+}

Task/Sum-multiples-of-3-and-5/JavaScript/sum-multiples-of-3-and-5-6.js

@@ -0,0 +1,3 @@
+for (var i=1, n=10; i<9; n*=10, i+=1) {
+	document.write(10, '<sup>', i, '</sup> ',  sm35(n), '<br>')
+}

Task/Sum-multiples-of-3-and-5/JavaScript/sum-multiples-of-3-and-5-7.js

@@ -0,0 +1,35 @@
+(() => {
+
+    // Area under straight line
+    // between first multiple and last
+    let sumMults = (n, factor) => {
+            let n1 = Math.floor((n - 1) / factor);
+
+            return Math.floor(factor * n1 * (n1 + 1) / 2);
+        },
+
+        sum35 = (n) => sumMults(n, 3) + sumMults(n, 5) - sumMults(n, 15);
+
+
+    // TEST
+
+    // range(intFrom, intTo, optional intStep)
+    // Int -> Int -> Maybe Int -> [Int]
+    let range = (m, n, step) => {
+        let d = (step || 1) * (n >= m ? 1 : -1);
+
+        return Array.from({
+            length: Math.floor((n - m) / d) + 1
+        }, (_, i) => m + (i * d));
+    }
+
+    // Sums for 10^1 thru 10^8
+
+    return range(1, 8)
+        .map(n => Math.pow(10, n))
+        .reduce((a, x) => (
+            a[x.toString()] = sum35(x),
+            a
+        ), {});
+
+})();

Task/Sum-multiples-of-3-and-5/JavaScript/sum-multiples-of-3-and-5-8.js

@@ -0,0 +1,3 @@
+{"10":23, "100":2318, "1000":233168, "10000":23331668,
+"100000":2333316668, "1000000":233333166668, "10000000":23333331666668,
+"100000000":2333333316666668}