diff --git a/01/app.js b/01/app.js
index e69de29..eec84ec 100644
--- a/01/app.js
+++ b/01/app.js
@@ -0,0 +1,6 @@
+function showTime() {
+	const time = new Date().toLocaleTimeString();
+	console.log(time);
+}
+
+showTime();
diff --git a/02/app.js b/02/app.js
index e69de29..388422c 100644
--- a/02/app.js
+++ b/02/app.js
@@ -0,0 +1,6 @@
+function sayHello(name) {
+	console.log(`Cześć ${name}!`);
+}
+
+sayHello('devmentor.pl');
+sayHello('Magda');
diff --git a/03/app.js b/03/app.js
index e69de29..da54e86 100644
--- a/03/app.js
+++ b/03/app.js
@@ -0,0 +1,22 @@
+const sum = function (number) {
+	let result = 0;
+	if (number >= 0) {
+		for (let i = 0; i <= number; i++) {
+			result += i;
+		}
+	} else {
+		for (let i = 0; i >= number; i--) {
+			result += i;
+		}
+	}
+
+	return result;
+};
+
+console.log(sum(4));
+console.log(sum(-4));
+console.log(sum(0));
+console.log(sum(10));
+console.log(sum(-10));
+console.log(sum(1));
+console.log(sum(-1));
diff --git a/04/app.js b/04/app.js
index e69de29..08c0e6c 100644
--- a/04/app.js
+++ b/04/app.js
@@ -0,0 +1,14 @@
+let counter = 0;
+
+const interval = setInterval(runTimer, 5000);
+
+function runTimer() {
+	const time = new Date().toLocaleTimeString();
+	console.log(time);
+
+	counter++;
+
+	if (counter >= 5) {
+		clearInterval(interval);
+	}
+}