Add a function to decide what type a unit is

Custom attributes will take string input and then decide if it is an acceptable
type of unit.

macrovision.js

@@ -75,6 +75,42 @@ let ratioInfo;
 
 //#region units
 
+function dimsEqual(unit1, unit2) {
+    a = unit1.dimensions;
+    b = unit2.dimensions;
+
+    if (a.length != b.length) {
+        return false;
+    }
+
+    for (let i = 0; i < a.length && i < b.length; i++) {
+        if (a[i] != b[i]) {
+            return false;
+        }
+    }
+
+    return true;
+}
+
+// Determines if a unit is one of a length, area, volume, mass, or energy
+function typeOfUnit(unit) {
+    if (dimsEqual(unit, math.unit(1, "meters"))) {
+        return "length"
+    }
+    if (dimsEqual(unit, math.unit(1, "meters^2"))) {
+        return "area"
+    }
+    if (dimsEqual(unit, math.unit(1, "meters^3"))) {
+        return "volume"
+    }
+    if (dimsEqual(unit, math.unit(1, "kilograms"))) {
+        return "mass"
+    }
+    if (dimsEqual(unit, math.unit(1, "joules"))) {
+        return "energy"
+    }
+}
+
 math.createUnit({
     ShoeSizeMensUS: {
         prefixes: "long",