client - forum page - pagination / threads per page

client/app/util/index.ts

@@ -1 +1,2 @@
 export * from './oauth/oauth';
+export * from './pagination/pagination';

client/app/util/pagination/pagination.ts

@@ -0,0 +1,30 @@
+export const pagination = (page: number, numPages: number): (number | string)[] => {
+  const current = page;
+  const last = numPages;
+  const delta = 2;
+  const left = current - delta;
+  const right = current + delta + 1;
+  const range = [];
+  const rangeWithDots = [];
+  let l;
+
+  for (let i = 1; i <= last; i++) {
+    if (i === 1 || i === last || (i >= left && i < right)) {
+      range.push(i);
+    }
+  }
+
+  for (const i of range) {
+    if (l) {
+      if (i - l === 2) {
+        rangeWithDots.push(l + 1);
+      } else if (i - l !== 1) {
+        rangeWithDots.push('...');
+      }
+    }
+    rangeWithDots.push(i);
+    l = i;
+  }
+
+  return rangeWithDots;
+};