allow for custom default value in series prev/next functions (#230)

* allow for default value in series prev/next

* bump version -> 10.6.0

cdn/radash.esm.js

@@ -761,18 +761,21 @@ const series = (items, toKey = (item) => `${item}`) => {
   const last = () => {
     return itemsByIndex[items.length - 1];
   };
-  const next = (current) => {
-    return itemsByIndex[indexesByKey[toKey(current)] + 1] ?? first();
+  const next = (current, defaultValue) => {
+    return itemsByIndex[indexesByKey[toKey(current)] + 1] ?? defaultValue ?? first();
   };
-  const previous = (current) => {
-    return itemsByIndex[indexesByKey[toKey(current)] - 1] ?? last();
+  const previous = (current, defaultValue) => {
+    return itemsByIndex[indexesByKey[toKey(current)] - 1] ?? defaultValue ?? last();
   };
   const spin = (current, num) => {
     if (num === 0)
       return current;
     const abs = Math.abs(num);
     const rel = abs > items.length ? abs % items.length : abs;
-    return list(0, rel - 1).reduce(num > 0 ? next : previous, current);
+    return list(0, rel - 1).reduce(
+      (acc) => num > 0 ? next(acc) : previous(acc),
+      current
+    );
   };
   return {
     min,

cdn/radash.js

@@ -764,18 +764,21 @@ var radash = (function (exports) {
     const last = () => {
       return itemsByIndex[items.length - 1];
     };
-    const next = (current) => {
-      return itemsByIndex[indexesByKey[toKey(current)] + 1] ?? first();
+    const next = (current, defaultValue) => {
+      return itemsByIndex[indexesByKey[toKey(current)] + 1] ?? defaultValue ?? first();
     };
-    const previous = (current) => {
-      return itemsByIndex[indexesByKey[toKey(current)] - 1] ?? last();
+    const previous = (current, defaultValue) => {
+      return itemsByIndex[indexesByKey[toKey(current)] - 1] ?? defaultValue ?? last();
     };
     const spin = (current, num) => {
       if (num === 0)
         return current;
       const abs = Math.abs(num);
       const rel = abs > items.length ? abs % items.length : abs;
-      return list(0, rel - 1).reduce(num > 0 ? next : previous, current);
+      return list(0, rel - 1).reduce(
+        (acc) => num > 0 ? next(acc) : previous(acc),
+        current
+      );
     };
     return {
       min,

package.json

@@ -1,6 +1,6 @@
 {
   "name": "radash",
-  "version": "10.5.0",
+  "version": "10.6.0",
   "description": "Functional utility library - modern, simple, typed, powerful",
   "main": "dist/cjs/index.cjs",
   "module": "dist/esm/index.mjs",

src/series.ts

@@ -55,16 +55,20 @@ export const series = <T>(
    * in the series or default if the given value is
    * the last item in the series
    */
-  const next = (current: T): T => {
-    return itemsByIndex[indexesByKey[toKey(current)] + 1] ?? first()
+  const next = (current: T, defaultValue?: T): T => {
+    return (
+      itemsByIndex[indexesByKey[toKey(current)] + 1] ?? defaultValue ?? first()
+    )
   }
   /**
    * Given an item in the series returns the previous item
    * in the series or default if the given value is
    * the first item in the series
    */
-  const previous = (current: T): T => {
-    return itemsByIndex[indexesByKey[toKey(current)] - 1] ?? last()
+  const previous = (current: T, defaultValue?: T): T => {
+    return (
+      itemsByIndex[indexesByKey[toKey(current)] - 1] ?? defaultValue ?? last()
+    )
   }
   /**
    * A more dynamic method than next and previous that
@@ -76,7 +80,10 @@ export const series = <T>(
     if (num === 0) return current
     const abs = Math.abs(num)
     const rel = abs > items.length ? abs % items.length : abs
-    return list(0, rel - 1).reduce(num > 0 ? next : previous, current)
+    return list(0, rel - 1).reduce(
+      acc => (num > 0 ? next(acc) : previous(acc)),
+      current
+    )
   }
   return {
     min,

src/tests/series.test.ts

@@ -56,6 +56,10 @@ describe('series module', () => {
       const result = sut.next('friday')
       assert.equal(result, 'monday')
     })
+    test('returns the given default when the last is exhausted', () => {
+      const result = sut.next('friday', 'wednesday')
+      assert.equal(result, 'wednesday')
+    })
   })
 
   describe('previous function', () => {
@@ -67,6 +71,10 @@ describe('series module', () => {
       const result = sut.previous('monday')
       assert.equal(result, 'friday')
     })
+    test('returns the given default when the first is exhausted', () => {
+      const result = sut.previous('monday', 'wednesday')
+      assert.equal(result, 'wednesday')
+    })
   })
 
   describe('spin function', () => {