Second take at Hello Mouse! and refactor some things into utils.js

utils.js

@@ -0,0 +1,47 @@
+/// A simple two-dimensional Cartesian Point.
+class Point {
+    constructor(x, y) {
+        this.x = x;
+        this.y = y;
+    }
+
+    length() {
+        return Math.sqrt(this.x * this.x + this.y * this.y);
+    }
+
+    normalize() {
+        let length = this.length();
+        this.x = this.x / length;
+        this.y = this.y / length;
+    }
+
+    scale(factor) {
+        this.x = this.x * factor;
+        this.y = this.y * factor;
+    }
+
+    /// Compute the Euclidean distance between @c this.point and the argument.
+    /// @see https://en.wikipedia.org/wiki/Euclidean_distance
+    distanceTo(point) {
+        let x = this.x - point.x;
+        let y = this.y - point.y;
+        return Math.sqrt(x * x + y * y);
+    }
+}
+
+const Clamp = {
+    Yes: 1,
+    No: 0,
+}
+
+/// Map an input value in an input range to a value in the output range.
+/// @see https://stackoverflow.com/questions/5731863/mapping-a-numeric-range-onto-another
+function mapValueInRangeToRange(input, inputStart, inputEnd, outputStart, outputEnd, clamp = Clamp.No) {
+    let mappedValue = outputStart + ((outputEnd - outputStart) / (inputEnd - inputStart)) * (input - inputStart);
+
+    if (clamp == Clamp.Yes) {
+        mappedValue = Math.min(outputEnd, Math.max(outputStart, mappedValue));
+    }
+
+    return mappedValue;
+}