Stylized console logging

Question

When I\'m on Facebook and have the console open, I see this image below. How do they do this?

Answer 1

Just like in Firebug you can use %c to style console log output. Look how we could implement Facebook's example:

console.log("%cStop!", "color: red; font-family: sans-serif; font-size: 4.5em; font-weight: bolder; text-shadow: #000 1px 1px;");

Since it supports CSS properties, we can even "draw" images in there:

(function(url) {
  // Create a new `Image` instance
  var image = new Image();

  image.onload = function() {
    // Inside here we already have the dimensions of the loaded image
    var style = [
      // Hacky way of forcing image's viewport using `font-size` and `line-height`
      'font-size: 1px;',
      'line-height: ' + this.height + 'px;',

      // Hacky way of forcing a middle/center anchor point for the image
      'padding: ' + this.height * .5 + 'px ' + this.width * .5 + 'px;',

      // Set image dimensions
      'background-size: ' + this.width + 'px ' + this.height + 'px;',

      // Set image URL
      'background: url('+ url +');'
     ].join(' ');

     // notice the space after %c
     console.log('%c ', style);
  };

  // Actually loads the image
  image.src = url;
})('https://i.cloudup.com/Zqeq2GhGjt-3000x3000.jpeg');

Answer 2

I wrapped this solution in a nice library:

https://www.npmjs.com/package/console-log-img

It can also display images from a Canvas or Image element, ImageBitmap and more!

Answer 3

For those who have two images, repeated, add background no-repeat as @BayyMekenique says but also change this line:

code 'line-height: ' + this.height + 'px;', code

to this:

code 'line-height: ' + this.height % 2 + 'px;', code