add providers filter to runBackupCycle

1 files changed, 15 insertions, 0 deletions

diff --git a/packages/taler-util/src/helpers.ts b/packages/taler-util/src/helpers.ts
index 53a9a43d4..089602c9d 100644
--- a/packages/taler-util/src/helpers.ts
+++ b/packages/taler-util/src/helpers.ts
@@ -110,3 +110,18 @@ export function strcmp(s1: string, s2: string): number {
 export function j2s(x: any): string {
   return JSON.stringify(x, undefined, 2);
 }
+
+/**
+ * Use this to filter null or undefined from an array in a type-safe fashion
+ * 
+ * example:
+ * const array: Array<T | undefined> = [undefined, null]
+ * const filtered: Array<T> = array.filter(notEmpty)
+ * 
+ * @param value 
+ * @returns 
+ */
+export function notEmpty<T>(value: T | null | undefined): value is T {
+  return value !== null && value !== undefined;
+}
+