Today I Learned

Conditionally add properties to objects in JavaScript

This comes in handy when you want to completely omit a property from an object in case the value is undefined or null.

{prop1, prop2, ...(condition && prop3)}

The trick being here:

...(condition && prop3)

In case the condition evaluates to false, the property will be completely omitted from the object, otherwise, both the value and its corresponding key will show up in the end result.

Correctly grouping members within modules in JSDoc v3

JSDoc is great! It's documentation not so much. I needed a way to logically group together global methods and I was unsuccessful in finding a straightforward way in its official documentation.

Eventually, I've come across the following method, using @module and @member.

First, we define the module name, usually at the top of the file:

@module MyModule

We then proceed to annotate the target function with @memeber MyModule. One other important aspect is to also include @function along with the name of the function in order to appear in the module section.

 * @member MyModule
 * @function myFunction
 export const myFunction = () => ....

How to set srcset and sizes attributes for responsive images

The default src attribute acts as fallback for a default image size for browsers that have no support for srcset:

<img src="/images/image.jpg">

The srcset attribute gives the browser a bunch of different sizes of the same image to choose from.

The name of the image doesn't matter, you could name them image-small, image-medium and so on, but the 375w part should match the real width of the image:

    srcset="/images/image-375.jpg 375w,
            /images/image-768.jpg 768w,
            /images/image-1440.jpg 1440w,
            /images/image-1920.jpg 1920w,
            /images/image-2560.jpg 2560w"

Adding the sizes attribute specifies what image size to choose at a specific breakpoint and above (min-width) or below (max-width) it:

    srcset="/images/image-375.jpg 375w,
            /images/image-768.jpg 768w,
            /images/image-1440.jpg 1440w,
            /images/image-1920.jpg 1920w,
            /images/image-2560.jpg 2560w"
    sizes="(min-width: 1920px) 1400px, (min-width: 1600px) 1000px, (min-width: 768px) 700px, 300px"

One thing to note here is that the browser will first calculate the device width and then look at the sizes attribute and choose the first matching condition.

If you set for example sizes="(max-width: 1920px) 1500px, (max-width: 768px) 600px, 300px", and the device width is 640px, the first matching condition will be max-width: 1920px, therefore it will choose the 1500px image width suggestion, rather than the 600 you most probably expected. The same can happen with the min-width if the order is not right.

Notice also that we are asking the browser to choose a 1000px wide image between 1600px and 1919px, but in the srcset sources, there's no image at 1000px. Here, the browser will choose the image with the exact size, if there is one, or the closest one if not, but higher in size than specified, in this case, 1000px. Therefore, the 1440px will be selected.

It can take a while to grasp how this works, but it's worth taking the time to understand it.

Postman Automatic Auth Token

Postman can run JavaScript commands when executing a request. These commands can be placed in the "Tests" tab inside a request. For example, to automatically set a token as a collection variable, the following commands are used:

var auth = pm.response.headers.get("Authorization");
pm.collectionVariables.set('token', auth.split(" ")[1]);

The Docs regarding Postman scripting can be found here:


Automate the creation and deletion of EC2 snapshots via AWS CLI 2

We're heavily using AWS and we're scripting everything we can. As AWS CLI 2 came out recently we needed to update our scripts.

This script creates a new snapshot and deletes all snapshots older than 2 weeks, for a specific volume.




SNAPSHOT_AGE=$(date +%Y-%m-%d --date '2 weeks ago')
TODAY=$(date +%d-%m-%Y)

echo "Creating new snapshot of volume $VOLUME."
aws ec2 create-snapshot --output text --description "$DESCRIPTION - AutoSnapshot $TODAY" --volume-id $VOLUME >> /dev/null

echo "Deleting snapshots older than: $SNAPSHOT_AGE"

snapshots=$(aws ec2 describe-snapshots --output text --filters Name=volume-id,Values=$VOLUME --query "Snapshots[?StartTime<'$SNAPSHOT_AGE'].SnapshotId")

echo "Snapshots sheduled for deletion: $snapshots"

for snapshot in $snapshots; do
  echo "Deleting $snapshot ..."
  aws ec2 delete-snapshot --snapshot-id $snapshot

Check composer platform requirements

If you ever need to check what php version do composer packages and their dependencies require, there's a special command just for that.

composer check-platform-reqs

The output should look something like below. Maybe without the failed steps.

ext-dom        20031129                                                success  
ext-fileinfo    7.3.19                                                  success  
ext-filter      7.3.19                                                  success  
ext-json       1.7.0                                                   success  
ext-libxml     7.3.19                                                  success  
ext-mbstring   7.3.19                                                  success  
ext-openssl    7.3.19                                                  success  
ext-pcre       7.3.19                                                  success  
ext-Phar       7.3.19                                                  success  
ext-SimpleXML  7.3.19                                                  success  
ext-tokenizer  7.3.19                                                  success  
ext-xml        7.3.19                                                  success  
ext-xmlwriter  7.3.19                                                  success  
lib-pcre       10.32                                                   success  
php            7.3.19    league/commonmark requires php (^7.4 || ^8.0) failed   
php            7.3.19    league/config requires php (^7.4 || ^8.0)      failed   

This is useful when your app fails due to unfulfilled dependency requirements.

Automatically add and remove SSH keys from remote hosts

Managing multiple hosts is a pain when using SSH key authentication. There are a lot of solutions out there for managing SSH keys, there's Ansible, Puppet, or other paid solutions.

There's also another option, to use a script to do the job for you.

Here's how

1. Create a targets file containing your hosts and usernames

# Host
hostname.example.com username

2. Create a add-keys.sh file

echo update ssh-keys: ${keys}

cat targets | grep -vE '^(\s*$|#)' | sed 's/#.*$//g' | while read host user
   echo "# Adding public ssh-keys for $user@$host"
   for k in ${keys};
      echo "# Adding public key $k"
      touch ${k%\.pub}
      ssh-copy-id -f -i $k $user@$host

3. Create a remove-keys.sh file


echo update ssh-keys: ${keys}

cat targets | grep -vE '^(\s*$|#)' | sed 's/#.*$//g' | while read host user
   echo "# Remove public ssh-keys for $user@$host"
   for k in ${keys};
      echo "# Remove public key $k"
      ssh $user@$host 'bash -s' <<EOT
sed -i "/$key/d" ~/.ssh/authorized_keys
      echo "# Key removed"

4. Add the public keys you want to add as .pub files in the same folder

5. Run one of the scripts. Done.