Refactor area into a separate module

src/conversion/area/_area.js

@@ -0,0 +1,39 @@
+const shared = require('../shared');
+
+function areaMap(imperialInputs, metricTransform) {
+  const metresSquared = imperialInputs.map(metricTransform);
+
+  const unitDecider = Math.max(...metresSquared);
+
+  let unitTransform = undefined;
+  let unit = undefined;
+
+  if (unitDecider >= 1000000) {
+    unitTransform = i => i / 1000000;
+    unit = " km^2";
+
+  } else if (unitDecider >= 10000) {
+    unitTransform = i => i / 10000;
+    unit = " hectares";
+
+  } else {
+    unitTransform = i => i;
+    unit = " m^2";
+  }
+
+  return shared.createMap(metresSquared, unitTransform, unit);
+}
+
+const metricAreaUnits = [
+      /square kilometers?/,
+      /sq\.? km/,
+      /sq\.? kilometers?/,
+      /km[^]2/,
+      /hectares/,
+      /m^2/
+    ];
+
+module.exports = {
+  "toMap" : areaMap,
+  "metricUnits" : metricAreaUnits
+}

src/conversion/area/acres.js

@@ -0,0 +1,11 @@
+const shared = require('../shared');
+const area = require('./_area');
+
+module.exports = {
+    "imperialUnits" : [/acres?/],
+    "standardInputUnit" : " acres",
+    "isInvalidInput" : shared.isZeroOrNegative,
+    "isWeaklyInvalidInput" : shared.isHyperbole,
+    "conversionFunction" : (i) => area.toMap(i, (j) => j * 4046.8564),
+    "ignoredUnits" : area.metricUnits
+  }

src/conversion_helper.js

@@ -1,19 +1,6 @@
 const rh = require('./regex_helper');
 const fsh = require('./file_system_helper');
 
-function areaMap(m2) {
-  const unitDecider = Math.max(...m2);
-  if (unitDecider >= 1000000) {
-    return createMap(m2.map((i) => i / 1000000), " km^2");
-
-  } else if (unitDecider >= 10000) {
-    return createMap(m2.map((i) => i / 10000), " hectares");
-
-  } else {
-    return createMap(m2, " m^2");
-  }
-}
-
 function pressureMap(pa) {
   const unitDecider = Math.max(...pa);
   if (unitDecider < 1000) {
@@ -185,19 +172,6 @@ let unitLookupList = [
       }
     },
     "ignoredUnits" : [/° ?C/, "degrees? c", "celsius", "kelvin"]
-  },
-  {
-    "imperialUnits" : [/acres?/],
-    "standardInputUnit" : " acres",
-    "isInvalidInput" : isZeroOrNegative,
-    "isWeaklyInvalidInput" : isHyperbole,
-    "conversionFunction" : (i) => areaMap(i.map((j) => j * 4046.8564)),
-    "ignoredUnits" : [
-      /square kilometers?/,
-      /sq.? km/,
-      /sq.? kilometers?/,
-      /km[^]2/
-    ]
   }
 ];