Init (#1)

backend/utils/limit-queue.ts

@@ -0,0 +1,24 @@
+/**
+ * Limit Queue
+ * The first element will be removed when the length exceeds the limit
+ */
+export class LimitQueue<T> extends Array<T> {
+    __limit;
+    __onExceed = null;
+
+    constructor(limit: number) {
+        super();
+        this.__limit = limit;
+    }
+
+    push(value : T) {
+        super.push(value);
+        if (this.length > this.__limit) {
+            const item = this.shift();
+            if (this.__onExceed) {
+                this.__onExceed(item);
+            }
+        }
+    }
+
+}