It’s a demo-less post. Nothing to show but a lot to explain. We are going to play with the console.

Before this challenge, I only made use of console.log for debugging. To me, that was enough to make sure the outputs of certain program, but there are other built-in methods from native console object available to help us eradicate bugs and errors. We are going to make the most of it.

To increase my own understanding, I’ll take all examples here personal. I hope you don’t mind.

Regular Logging

This is regular console.log we often encounter in our spaghetti code.

  console.log("Are you here with me?");

With Interpolation

Sometime we need to insert value between text consumed by console.log. Well, what for? To make it easier to change later on!

  (function () {
    var her = 'ちえさ せれな';

    // PHP style
    console.log("is %s here with me?", her);

    // ES6 style
    console.log(`is ${her} here with me?`);

Styling The Text

If we would love to emphasize text with color and style, don’t hesitate. Nike says, “Just do it!”

  (function () {
    var her = "メリー メディオーアティ";
    console.log(`%c ${her} is the best ❤`, "color: pink; font-size: 25px;")

You will see this in console.

メリー メディオーアティ is the best ❤

Pay attention. %c before text indicates the text are going to be styled with inline CSS we pass to second parameter.


Instead of simply “say what you say” via console.log, what if we warn our users about the one we care the most?

  (function () {
    var her = "ちえさ せれな";
    console.warn(`Don't touch ${her}`);


We’ve warned users before, don’t you think we need to kindly inform users about something too?

  (function () {
    var her = "ちえさ せれな";`I don't own ${her} but I want to hold her hand and kiss \
     her on the cheek like she did to me in my dream`);


We also can check the truth via console. It’s quite useful.

  console.assert("I hate a lot of people but I don't hate you" === "I like you",
    "We both know that's bullshit darling... I really like you.")

console.assert only display text whenever the condition false like that expression above. Of course I like ちえさ せれな, I mean it!

Displaying Error

Enough warning, enough conveying, just tell the users that we made a terrible mistake even if it was a beautiful mistake! Error! Error! Error!

  console.error("I love メリー メディオーアティ, that's a mistake, a beautiful mistake...");


Back then, I liked ちえさ せれな, really liked her. Now, I want to forget that feeling… It’s going to be cleared away… Hopefully.

  console.log('I liked ちえさ せれな');


How long does it take to fetch my profile from github?

  // We start here...
    .then(function (blob) {
      return blob.json();
    .then(function (data) {
      // We end the timer when we've actually fetched the data...
      console.timeEnd('fetching data from');


The last one, I want to group my crushes with pride!

Here’s my girls!

  var crushes = [
      name: "ルル オーリア",
      age: 25,
      status: "single",
      tags: "cute, sexy, hypocrite, obnoxious"

      name: "メリー メディオーアティ",
      age: 26,
      status: "married",
      tags: "cute, pious, intelligent"

      name: "ちえさ せれな",
      age: 23,
      status: "single",
      tags: "cute, fragile, sensitive, emotional"

Here’s how it should be done!

  (function () {
    crushes.forEach(function (crush) {
      console.log(`I like ${}`);
      console.log(`She is ${crush.age} years old`);

Copy-paste all the snippets above and run in console. CTRL + SHIFT + i to open the console.

Okay, that’s it for today. Until tomorrow.