fix: throw TypeError if onEvict callback is not a function

Author: avoidwork

coverage.txt

@@ -3,8 +3,8 @@
 ℹ file      | line % | branch % | funcs % | uncovered lines
 ℹ ----------------------------------------------------------
 ℹ src       |        |          |         | 
-ℹ  lru.js   | 100.00 |    98.54 |  100.00 | 
+ℹ  lru.js   |  99.70 |    98.54 |  100.00 | 534-535
 ℹ ----------------------------------------------------------
-ℹ all files | 100.00 |    98.54 |  100.00 | 
+ℹ all files |  99.70 |    98.54 |  100.00 | 
 ℹ ----------------------------------------------------------
 ℹ end of coverage report

src/lru.js

@@ -126,7 +126,7 @@ export class LRU {
 
 		item.prev = null;
 		item.next = null;
-		if (typeof this.#onEvict === "function") {
+		if (this.#onEvict !== null) {
 			this.#onEvict({
 				key: item.key,
 				value: item.value,
@@ -530,7 +530,11 @@ export class LRU {
 	 * @returns {LRU} The LRU instance for method chaining.
 	 */
 	onEvict(callback) {
-		this.#onEvict = typeof callback === "function" ? callback : null;
+		if (typeof callback !== "function") {
+			throw new TypeError("onEvict callback must be a function");
+		}
+
+		this.#onEvict = callback;
 
 		return this;
 	}