Implement toDistrict

Document & add deploy on instance method

Author: cblanc

lib/index.ts

@@ -29,7 +29,6 @@ const matchOn = (s: string, regex: RegExp): RegExpMatchArray | null => {
 
 const incodeRegex = /\d[a-z]{2}$/i;
 const validOutcodeRegex = /^[a-z]{1,2}\d[a-z\d]?$/i;
-const districtSplitRegex = /^([a-z]{1,2}\d)([a-z])$/i;
 const VALIDATION_REGEX = /^[a-z]{1,2}\d[a-z\d]?\s*\d[a-z]{2}$/i;
 
 /**
@@ -121,6 +120,28 @@ const toUnit: Parser = postcode => {
   return firstOrNull(match);
 };
 
+const DISTRICT_SPLIT_REGEX = /^([a-z]{1,2}\d)([a-z])$/i;
+
+/**
+ * Returns a correctly formatted district given a postcode
+ *
+ * Returns null if invalid postcode
+ *
+ * @example
+ *
+ * ```
+ * toDistrict("AA9") // => "AA9"
+ * toDistrict("A9A") // => "A9"
+ * ```
+ */
+const toDistrict: Parser = postcode => {
+  const outcode = toOutcode(postcode);
+  if (outcode === null) return null;
+  const match = outcode.match(DISTRICT_SPLIT_REGEX);
+  if (match === null) return outcode;
+  return match[1];
+};
+
 const returnNull = () => null;
 
 /**
@@ -168,6 +189,7 @@ class Postcode {
   static toArea = toArea;
   static toSector = toSector;
   static toUnit = toUnit;
+  static toDistrict = toDistrict;
 
   static validOutcode(outcode: string): boolean {
     return outcode.match(validOutcodeRegex) !== null;
@@ -196,21 +218,16 @@ class Postcode {
   }
 
   district(): string | null {
-    if (!this._valid) return null;
     if (this._district) return this._district;
-    const outcode = this.outcode();
-    if (outcode === null) return null;
-    const split = outcode.match(districtSplitRegex);
-    this._district = split !== null ? split[1] : outcode;
-    return this._district;
+    return (this._district = toDistrict(this._raw));
   }
 
   subDistrict(): string | null {
     if (!this._valid) return null;
     if (this._subDistrict) return this._subDistrict;
     const outcode = this.outcode();
     if (outcode === null) return null;
-    const split = outcode.match(districtSplitRegex);
+    const split = outcode.match(DISTRICT_SPLIT_REGEX);
     this._subDistrict = split !== null ? outcode : null;
     return this._subDistrict;
   }

test/statics.unit.ts

@@ -72,16 +72,16 @@ describe("Postcode.toArea", () => {
   });
 });
 
-// describe("Postcode.toDistrict", () => {
-//   it("should correctly parse districts", async () => {
-//     const { tests } = await loadFixtures("districts.json");
-//     testMethod({ method: Postcode.toDistrict, tests });
-//   });
+describe("Postcode.toDistrict", () => {
+  it("should correctly parse districts", async () => {
+    const { tests } = await loadFixtures("districts.json");
+    testMethod({ method: Postcode.toDistrict, tests });
+  });
 
-//   it("should return undefined if invalid postcode", () => {
-//     assert.isNull(Postcode.toDistrict("Definitely bogus"));
-//   });
-// });
+  it("should return undefined if invalid postcode", () => {
+    assert.isNull(Postcode.toDistrict("Definitely bogus"));
+  });
+});
 
 // describe("Postcode.toSubDistrict", () => {
 //   it("should correctly parse sub-districts", async () => {