new "empty" sugar.js util

3 files changed, 25 insertions, 6 deletions

diff --git a/src/util/sugar.js b/src/util/sugar.js
index c836d0ce..24ae8639 100644
--- a/src/util/sugar.js
+++ b/src/util/sugar.js
@@ -30,6 +30,20 @@ export function* splitArray(array, fn) {
   }
 }
 
+// Null-accepting function to check if an array is empty. Accepts null (and
+// treats as empty) as a shorthand for "hey, check if this property is an array
+// with/without stuff in it" for objects where properties that are PRESENT but
+// don't currently have a VALUE are null (instead of undefined).
+export function empty(arrayOrNull) {
+  if (arrayOrNull === null) {
+    return true;
+  } else if (Array.isArray(arrayOrNull)) {
+    return arrayOrNull.length === 0;
+  } else {
+    throw new Error(`Expected array or null`);
+  }
+}
+
 // Sums the values in an array, optionally taking a function which maps each
 // item to a number (handy for accessing a certain property on an array of like
 // objects). This also coalesces null values to zero, so if the mapping function
diff --git a/src/util/urls.js b/src/util/urls.js
index 45ec4c85..d86c047d 100644
--- a/src/util/urls.js
+++ b/src/util/urls.js
@@ -11,6 +11,7 @@
 // the domain of link.js.
 
 import * as path from 'path';
+
 import {withEntries} from './sugar.js';
 
 export function generateURLs(urlSpec) {
diff --git a/src/util/wiki-data.js b/src/util/wiki-data.js
index 97ffab76..b0b0b2e0 100644
--- a/src/util/wiki-data.js
+++ b/src/util/wiki-data.js
@@ -2,6 +2,8 @@
 
 // Utility functions for interacting with wiki data.
 
+import {empty} from './sugar.js';
+
 // Generic value operations
 
 export function getKebabCase(name) {
@@ -16,9 +18,11 @@ export function getKebabCase(name) {
 }
 
 export function chunkByConditions(array, conditions) {
-  if (array.length === 0) {
+  if (empty(array)) {
     return [];
-  } else if (conditions.length === 0) {
+  }
+
+  if (empty(conditions)) {
     return [array];
   }
 
@@ -469,7 +473,7 @@ export function getNewAdditions(numAlbums, {wikiData}) {
     // Then cycle over that sorted array, adding one al8um from each to
     // the main array until we've run out or have met the target num8er
     // of al8ums.
-    while (groupArray.length) {
+    while (!empty(groupArray)) {
       let j = 0;
       while (j < groupArray.length) {
         const entry = groupArray[j];
@@ -485,10 +489,10 @@ export function getNewAdditions(numAlbums, {wikiData}) {
           break outerLoop;
         }
 
-        if (entry.length) {
-          j++;
-        } else {
+        if (empty(entry)) {
           groupArray.splice(j, 1);
+        } else {
+          j++;
         }
       }
     }