---
title: "Console Candy"
url: "https://www.bekk.christmas/post/2018/15/console-candy"
authors: ["Mikael Bjerga"]
published: "2018-12-15"
updated: "2024-11-07T13:05:28Z"
language: "en-US"
type: "article"
tags: ["JavaScript"]
---

# Console Candy

Why is Console.log everybody's favourite?

## In short

The console offers more than console.log: warnings, errors, assertions, counters, tables, grouped output, and timing tools that help surface what code is doing as it runs. With methods like groupCollapsed and %c styling, you can also organize and format console output to make debugging easier to follow.

- **For:** JavaScript developers who want to use the console more effectively
- **Good to know beforehand:** Basic familiarity with JavaScript and console.log

_AI-generated_

Do you remember that time when you wrote that piece of flawless code, which just ran perfectly and had no weird behaviour? Me neither. The truth is: stuff breaks. All the time. So it would be incredibly helpful if we could have some way of outputting stuff as it runs. Wait … we have? Sweet!

## What does the console say?

You probably already know about our trusty little helper `console` and his friend `log`. Want to print something to the console? Throw a `console.log` in there! Easy peasy.

```js
console.log("Parapapapa, I'm loggin' it");
```

But did you know that `console` is a really popular guy and has lots of other friends? They're tired of `log` getting all the attention, so let's get to know them too!

### Warnings and errors

`warn` and `error` are `log`'s cousins. They're both similar to `log`, but have their own personalities and a bit more flare. `warn` is fond of yellow and also puts a warning icon next to what you want to output. Pretty neat if you want something to stand out, like a warning!

```js
console.warn("DANGER ZONE!");
```

`error` is even more dramatic, preferring to output messages like errors, in classic oh-no-red and with a handy stack trace from where it was called. Jam it inside an if-clause to make sure those naughty variables aren't `undefined`, or contain any values they shouldn't.

```js
function ohNo() {
  console.error("Get to the choppa!");
}
```

### Assertions

If you like that scary red color, you could also ask `assert` to help. `assert` is rogue vigilante who roots out falsehoods wherever it finds them. If you give it a boolean expression, it'll let you know straight away if it evaluates to false, by kicking it in the shins and outputting the supersecret message you agreed on.

```js
const batmanScore = 98;
const supermanScore = 37;

const message = "Not the log we deserve, but the one we need right now";
console.assert(supermanScore > batmanScore, message, [
  supermanScore,
  batmanScore,
]);
```

### Counting

Another quirky comrade is `count`. `count` is like an obsessive version of `log`. It'll output what you give it, but it always keeps track of how many times that particular output has been printed. Also, because it's kind of a show off, it will tell you what that number is. Every. Darn. Time.

```js
reasonsToBeSad = [
  "Up",
  "I can't grow a beard",
  "The popularity of the song 'Despacito'",
];

for (const reason of reasonsToBeSad) {
  console.count("This is so sad. Alexa, play Despacito.");
}
```

### Tables

Do you like magic? Of course you do. Who doesn't? `table` is a bit of a magician. You give it some data and it'll transmogrify that data straight into a table, all McGonagall style. It doesn't even care if the data is an array or an object – it does both! This bad boy can fit so much data in it.

```js
const statistics = [
  { expected: "The Aquaman movie was good", pollData: "12%" },
  { expected: "Monday", pollData: "36%" },
  { expected: "The Spanish Inquisition", pollData: "0%" },
];

console.table(statistics);
```

### Groups

With all these console possibilities, it might get a bit hard to follow, right? Wrong! The grouping gang has your back. Just put anything in between `group` and `groupEnd`, and they'll make sure any console output in there gets grouped together. Are you a bit of a minimalist? Use `groupCollapsed` instead of `group` and you won't believe what happens next: the group output is collapsed by default!

```js
console.group("open");
console.log("now");
console.log("you");
console.log("see");
console.log("me");
console.groupEnd();

console.groupCollapsed("closed");
console.log("now");
console.log("you");
console.log("don't");
console.groupEnd();
```

### Timing

The last of `console`'s buddies we'll meet today is `time` and `timeEnd`. They're a couple of speed freaks and love to check how fast your code is. Put `time` in front, to bellow “START”, and `timeEnd` at the end, to yell “STOP”. Then they'll work out how good you did, and present your time in tiny milliseconds. What a **time** to be alive.

```js
console.time("Adventure time!");

for (let i = 0; i < 10000; i++) {
  console.log("What time is it?", i);
}

console.timeEnd("Adventure time!");
```

### … and those who must not be named

Now you know the gang! … Well, not all of them. Some are a bit shy, but if you head over to their [home](https://developer.mozilla.org/en-US/docs/Web/API/Console) I'm sure they'll introduce themselves.

### Bonus round!

Do you want your console to look a bit extra? Hit a string up with a `%c` and pass some CSS to make your output look all kinds of fancy!

```js
const css = "font-size: xx-large; color: white; background-color: blue;";
console.log("%cI'm blue, da ba dee da ba bye", css);
```

Merry middle of December y'all!

## Relevant resources recommended by the author

- [Console](https://developer.mozilla.org/en-US/docs/Web/API/Console)
- [Styling console output with CSS](https://developers.google.com/web/tools/chrome-devtools/console/console-write#styling_console_output_with_css)

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