done

01/app.js

@@ -0,0 +1,6 @@
+function showTime() {
+  const time = new Date().toLocaleTimeString();
+  console.log(time);
+}
+
+showTime();

02/app.js

@@ -0,0 +1,5 @@
+function sayHello(name) {
+  console.log(`Cześć ${name}.`);
+}
+
+sayHello("Michał");

03/app.js

@@ -0,0 +1,9 @@
+function sumPrevNumbers(number) {
+  let result = 0;
+  for (let i = 1; i <= number; i++) {
+    result += i;
+  }
+  return result;
+}
+
+console.log(sumPrevNumbers(5));

04/app.js

@@ -0,0 +1,14 @@
+const runTimer = function () {
+  let intervalNumber = 0;
+  let interval;
+
+  interval = setInterval(function () {
+    console.log(new Date().toLocaleTimeString());
+    intervalNumber++;
+    if (intervalNumber === 5) {
+      clearInterval(interval);
+    }
+  }, 5000);
+};
+
+runTimer();