Timers and Console

🕰️ Node.js Timers & Console: Your Kitchen Timer & Notepad

The Big Picture: What Are We Learning?

Imagine you’re in a kitchen. You have two super helpful tools:

1. A Kitchen Timer ⏲️ — It helps you do things later or again and again
2. A Notepad 📝 — You write down what’s happening so you don’t forget

In Node.js:

• Timers = Your kitchen timer (do stuff after waiting)
• Console = Your notepad (write messages to see what’s happening)

Let’s explore both!

🍳 PART 1: TIMERS — Doing Things Later

What Are Timers? (Overview)

Think about baking cookies. You put them in the oven and set a timer for 10 minutes. You don’t stand there staring — you go do other things! When the timer rings, you take them out.

Node.js timers work the same way:

• Tell Node.js to wait
• Then do something when time is up
• Meanwhile, Node.js can do other work!

// I'll say "Ding!" after 3 seconds
setTimeout(() => {
  console.log("Ding! Cookies ready!");
}, 3000);

console.log("Timer set, doing other stuff...");

What prints first? “Timer set, doing other stuff…” — because Node.js doesn’t wait around!

⏰ Setting Timers

Node.js gives you THREE types of timers:

1. setTimeout — “Do this ONCE after waiting”

Like setting an alarm that rings just once.

// Ring after 2 seconds (2000 milliseconds)
setTimeout(() => {
  console.log("Wake up!");
}, 2000);

Real-life example: A reminder to drink water in 1 hour.

2. setInterval — “Do this AGAIN and AGAIN”

Like a heartbeat — it keeps going at regular intervals.

// Tick every 1 second
setInterval(() => {
  console.log("Tick...");
}, 1000);

Real-life example: A clock that ticks every second.

3. setImmediate — “Do this RIGHT AFTER current work”

Like saying “I’ll do this next, but let me finish what I’m doing first.”

setImmediate(() => {
  console.log("Done immediately after!");
});

console.log("This prints first");

Output:

This prints first
Done immediately after!

🛑 Clearing Timers

What if you set a timer but change your mind? Cancel it!

Each set function returns an ID. Use that ID to cancel:

// Set a timer
const timerId = setTimeout(() => {
  console.log("This won't print!");
}, 5000);

// Cancel it before it fires
clearTimeout(timerId);
console.log("Timer cancelled!");

Story Time: 🍕 You ordered pizza (setTimeout). But then you found food at home. You cancel the order (clearTimeout). No pizza arrives!

Stopping a Repeating Timer

let count = 0;

const intervalId = setInterval(() => {
  count++;
  console.log(`Count: ${count}`);

  if (count === 3) {
    clearInterval(intervalId);
    console.log("Stopped counting!");
  }
}, 1000);

Output:

Count: 1
Count: 2
Count: 3
Stopped counting!

🎁 Timer Promises API

The Modern Way! 🚀

Old timers use callbacks. New timers can use async/await — much cleaner!

First, import from timers/promises:

import { setTimeout } from 'timers/promises';

async function cookDinner() {
  console.log("Cooking...");

  // Wait 2 seconds (no callback needed!)
  await setTimeout(2000);

  console.log("Dinner is ready!");
}

cookDinner();

Why is this better?

• No callback pyramids 🏔️
• Code reads top-to-bottom
• Easier to understand!

All Timer Promises

import {
  setTimeout,
  setInterval,
  setImmediate
} from 'timers/promises';

// setTimeout with value
const result = await setTimeout(1000, 'Hello!');
console.log(result); // 'Hello!'

// setImmediate
await setImmediate();
console.log('Ran immediately after!');

📝 PART 2: CONSOLE — Your Notepad

What Is Console? (Overview)

The console is like a notepad where you write messages. It helps you:

• See what your code is doing
• Find bugs (detective work! 🔍)
• Show information to developers

Every program needs a way to “talk” — console is how Node.js talks to you!

🖨️ Console Output

The console has different “pens” for different messages:

console.log — Regular Messages

console.log("Hello, World!");
console.log("The answer is", 42);
console.log("User:", { name: "Alex", age: 10 });

console.error — Something Went Wrong! 🚨

console.error("Oops! Something broke!");

Shows in red in most terminals.

console.warn — Be Careful! ⚠️

console.warn("This might cause problems...");

Shows in yellow in most terminals.

console.info — FYI 💡

console.info("Server started on port 3000");

Same as log, but shows you’re giving information.

console.debug — For Detectives 🔍

console.debug("Checking value:", someVariable);

Extra details for debugging.

📊 console.table — Pretty Tables!

When you have a list of things, console.table makes it beautiful:

const pets = [
  { name: "Max", type: "Dog", age: 3 },
  { name: "Whiskers", type: "Cat", age: 5 },
  { name: "Goldie", type: "Fish", age: 1 }
];

console.table(pets);

Output:

┌─────────┬───────────┬────────┬─────┐
│ (index) │   name    │  type  │ age │
├─────────┼───────────┼────────┼─────┤
│    0    │  'Max'    │ 'Dog'  │  3  │
│    1    │ 'Whiskers'│ 'Cat'  │  5  │
│    2    │ 'Goldie'  │ 'Fish' │  1  │
└─────────┴───────────┴────────┴─────┘

So much easier to read! 👀

You can also pick specific columns:

console.table(pets, ['name', 'type']);

⏱️ Console Timing — How Fast Is Your Code?

Want to know how long something takes? Use timing!

console.time & console.timeEnd

console.time('cooking');

// Simulate cooking (do some work)
for (let i = 0; i < 1000000; i++) {
  // cooking...
}

console.timeEnd('cooking');

Output:

cooking: 5.234ms

The label must match! Both use 'cooking'.

console.timeLog — Check Time Without Stopping

console.time('baking');

// Step 1
console.timeLog('baking', 'Mixed ingredients');

// Step 2
console.timeLog('baking', 'Put in oven');

// Done
console.timeEnd('baking');

Output:

baking: 1.2ms Mixed ingredients
baking: 2.5ms Put in oven
baking: 3.8ms

🎯 Quick Summary

graph LR
    A["Node.js Core Utilities"] --> B["⏰ Timers"]
    A --> C["📝 Console"]

    B --> D["setTimeout - Once"]
    B --> E["setInterval - Repeat"]
    B --> F["setImmediate - Next"]
    B --> G["clear* - Cancel"]
    B --> H["Promises API - Modern"]

    C --> I["log/error/warn"]
    C --> J["table - Pretty Data"]
    C --> K["time/timeEnd - Speed"]

🏆 You Did It!

You now know how to:

• ⏰ Make code wait with setTimeout
• 🔄 Repeat actions with setInterval
• 🛑 Cancel timers when you change your mind
• ✨ Use modern promises for cleaner code
• 📝 Print messages with console.log
• 📊 Make pretty tables with console.table
• ⏱️ Measure how fast your code runs

You’re now a Timer & Console expert! 🎉

Remember: Timers are your kitchen timer, Console is your notepad. Use them together to cook amazing Node.js programs! 🍳📝