Improve error message when not passing in a function for the first pa…

…rameter Closes #8
sindresorhus · Jun 21, 2024 · 69d2486 · 69d2486
1 parent cd2c05c
commit 69d2486
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diff --git a/index.js b/index.js
@@ -1,4 +1,10 @@
 function throttle(function_, wait) {
+	if (typeof function_ !== 'function') {
+		throw new TypeError(`Expected the first argument to be a \`function\`, got \`${typeof function_}\`.`);
+	}
+
+	// TODO: Add `wait` validation too in the next major version.
+
 	let timeoutId;
 	let lastCallTime = 0;
 

diff --git a/test.js b/test.js
@@ -279,3 +279,13 @@ test('throttled function handles system time changes', async t => {
 	await delay(wait);
 	t.is(count.callCount, 2, 'Should allow a call after wait time');
 });
+
+test('parameter validation', t => {
+	t.throws(() => {
+		throttle(undefined, 0);
+	}, {instanceOf: TypeError});
+
+	/// t.throws(() => {
+	// 	throttle(() => {});
+	// }, {instanceOf: TypeError});
+});