[#167] Expand textarea for sentence input; use untrack to break recursive reactivity loops hanging the page on long sentences; Use better error message instead of ERROR (#182)

src/lib/util/debounce.ts

@@ -0,0 +1,46 @@
+/**
+ * Creates a debounced function that delays invoking the provided function
+ * until after 'wait' milliseconds have elapsed since the last time it was
+ * invoked.
+ *
+ * I could use _.debounce(), but bringing dependency on lodash didn't feel
+ * justified yet.
+ * 
+ * @param func The function to debounce
+ * @param wait The number of milliseconds to delay execution
+ * @returns A debounced version of the provided function
+ */
+function debounce<T extends (...args: any[]) => void>(
+  func: T,
+  wait: number
+): T & { cancel: () => void } {
+  let timeout: ReturnType<typeof setTimeout> | null = null;
+
+  const debounced = function(
+    this: ThisParameterType<T>, ...args: Parameters<T>
+  ): void {
+    const context = this;
+
+    const later = function() {
+      timeout = null;
+      func.apply(context, args);
+    };
+
+    if (timeout) {
+      clearTimeout(timeout);
+    }
+
+    timeout = setTimeout(later, wait);
+  };
+
+  debounced.cancel = function() {
+    if (timeout) {
+      clearTimeout(timeout);
+      timeout = null;
+    }
+  };
+
+  return debounced as T & { cancel: () => void };
+}
+
+export default debounce;