Get a Unique List of Objects in an Array of Object in JavaScript

Recently, I needed a way to ensure that my JavaScript array of objects does not contain any duplicates objects based on an ‘id’ key. While I do enjoy more common approaches to this solution with the use of a simple for loop it is always a bit of fun to see how folks have come up with modern solutions.

It wasn’t too long before I stumbled across this ES6 one-liner:

Pretty neat, huh?

Here are too locations I found them:

But as many code oneliners are, they are a little tricky to understand. So I wanted to spend some to understanding how this worked and thought, you might find this a little interesting too.

Let’s take a look at an example and then work through each bit as we go.

 

The Example

In the example above, we want to create a unique array of objects based on the ‘name’ property of each object set.

You can see that there is a duplicate property in positions 1 and 4 with key ‘name’ and value, ‘Alessia Medina’ that we need to remove.

You can also change the key to either the ‘character’ or ‘episodes’ property.

When the distinct array of objects is created it will set the last duplicate object as the object value. Why? Because the script will essentially reassign the ‘name’ property each time it loops through the array when creating the new map.

Let’s start breaking down the script so we can see how each one operates.

Code Breakdown

myObjArray.map

The first task of this script remaps the array of objects using the JavaScript map() method. This method takes a function, which in our is an arrow function.

Map method arrow functions generally look like this:

As an ordinary function, it would look like this:

In our example above, we have our callback arguments on a new line so we will also need to include curly braces {}.

With the map method, the function will act on each array and return the result to generate a new array of the same length.

For us, our call back condition rebuilds each array to make a sub-array containing the value of each name key in the array as the zeroeth element and the object at the first element.

So the first element in the new array will look like this:

new Map

A quick side example

Before we continue, let’s take a quick look at a basic Map process on a 2d array:

To be frank, I didn’t really understand the Map object too well until I explored this script.

Map object stores key-value pairs similar to an Object. However, the Map maintains the insertion order of the properties. You’ll see Map objects often displayed like this when logged out in the console.

Map can be iterated through in a similar way to a 2d array with the zeroeth element as a key and the next element as a value for each property of the map – ['key', 'value'].

Alternatively, we can also generate a Map from a 2d array as we did in the example above – turning each sub-array into a key-value pair.

Back to our main example…

new Map of our example

We are using the data we retrieved from our previous example here to remove some of the clutter from the process. I have added those results at the top of the code block above.

In this example, we simply apply new Map to this array of data. By doing this Map turns into a type of Object with a key-value pair. Now keep in mind that Object keys are the highlander of data types – there can be only one.

What does this mean beyond a bad joke that really shows my age?

It means that each key must be unique. All of our keys are now the names of our users. The new Map constructor process with then iterate through each name and store it and then assign its value. If a key already exists it will overwrite it with this next value with the same key name.

This means that the last duplicate key will always be displayed. Effectively only storing unique values.

Displaying the keys of each property in the Map

We can generate iterators to go through each key or value with the keys() and values() methods respectively.

We will have a look at the keys() method first quickly.

Let’s apply keys() to our test_uniqueObjArray_NewMap Map we generated above.

As you can see this produces an iterator of all the (unique) keys in our data as a Map Iterator. It’s not quite an array of objects, but it allows us to iterate over each key to do something with it.

The same is true for the values() method.

Displaying the values of each property in the Map

Here we want to get an iterator of our values so that we can recreate an array of objects again.

Using the values() iterator method we now have our Map values ready to go.

Using the spread syntax to create our array of object

Now that we have an iterator of our unique values we can now place them in our spread syntax – “...“.

When you apply the spread syntax on an array, it will add each item of an iterable to the array. Take a look at what it does to our Map values.

This is similar to using the Array.from() static method that would look like this:

Performance

So how does this one-liner stack up against a more traditional for-loop like this?

Surprisingly better than I thought it would, to be honest.

Running a benchmark test with jsbench.me, the one-liner ran only 13.74% slower. Which is pretty good compared to some of the other options I found out there.

Conclusion

So should you be using this oneliner over the for loop? Is an impressive one-liner better than something more clear? To be honest, I am on the fence.

I do like the way this script operates. It is clean and once I got my head around the Map object, it did make a lot of sense. I think if I saw something like this in the wild I could pretty easily identify what it was for and see that it was a nice short solution to a problem.

I don’t think I would use this approach when I need to iterate over objects in the many thousands. Then speed becomes important. But if I need something in my toolkit to solve a problem like this, then I am definitely going to use it.

I have an example of how I used the code to check for duplicate selections of files in Google Drive here:

Create a Google Workspace Add-on file picker card with CardService that opens a Google Picker in an overlay window – Google Apps Script

 

What do you think? Is it too abstract or is it elegant?

Did this tutorial help you understand the JavaScript one-liner better? Do you think you would apply it in your own projects?

Please let me know your thoughts in the comments below. I really enjoy hearing how things are used in the wild.

 

Create Removable Item Buttons Generated From Select or Comma-separated Input elements with HTML, CSS and JS

I am currently working on a larger project at the moment that requires a lot of front-end wrangling. As a part of this project, I needed to create Button Items that are generated by the user from both an HTML select element for one section and, a comma-separated text input in another section.

When a user selects an item from a select menu, a button appears in a desired area with the name of the selection and a small “X” that can be clicked to remove the item. Likewise, if a user wishes to create a bunch of items separated by commas in an input element and either hit the “Enter” or the “Add” button, then those items will be transformed as a bunch of individual buttons that the user can remove and change.

The buttons essentially become the user’s selection of items.

I also needed to be able to get a list of those item buttons for when I submit a form server-side or for some other task.

As a result, I created a small library called itemButton().

Note: If you have a bit of experience with front-end, then all you may need is to grab the CSS code and input.js file. If you need some further explanation you can find the information below.

What it does

The itemButton() library:

  1. Creates a button named by the selection or the user’s input, This is removable should the user wish to change their choices.
  2. Allows you to select the max number of items you want your users to be able to choose.
  3. Easily extracts a list of buttons by ID and value.

An example

Take a look at an example:

My inability to consistently fail to place an ‘e’ at the end of giraffe notwithstanding, you can see that the user can select items from a select element and they will be displayed in a chosen area below. Further, when the user types some words and separates them by a comma they are displayed as buttons in a div below it.

Limit the number of displayed Item Buttons

You might have also noted that the select element will only display two-item buttons, while the comma-separated list will display up to 10. You are able to create a maximum limit of any of your text input or select elements you are running itemButton() on.

Validation

When the user submits their items, itemButton() will:

  • Check for duplicates. If it already exists, it won’t be displayed again.
  • Remove any empty comma-separated elements.
  • Remove any non-alphanumeric characters.
  • Cut any text input items between commas to less than or equal to 25 characters (You can change this if you want).
  • Exchange any spaces between words with a dash for the button ID.
  • Any item starting with a number gets and “a” at the start of the button ID so it can be used in the HTML.

Getting a list if item buttons

As you can see in the video above, when the user clicks the Log Items button, an object of ids and values for each item is listed in the browser console using the list() method in itemButton(). This is most useful for when you are submitting data to the server.

Let’s have a gander at the code:

The Code

I have chosen to put the Javascript itemButton() library in an input.js file. In my project,  I have other small classes or libraries in that file too. It is up to you how you want to add the code.

The CSS for the buttons is separate, and I have added it to my universal style.css file. Again you can put it anywhere you think works for you.

input.js

stlye.css

Add this to your main CSS file.

Quick use guide

Create the select button or input button

First, you will need to create your select or text input elements. Make sure that they have an appropriate ID that we can reference later.  You can have as many select or text input elements as you want to reference the itemButton() class.

Take a look at the example below:

Here we have added a select element with an id of “items”. We also have a text input with an ID of “tags”. The “tags” element also has an “addTag” button that the user can use to add their tags.

Create a div or span for your item buttons to go

Next, we need to create a location to display your item buttons. In the example below, I have used a div directly below the select or input elements.

Importing the itemButton() code

Our next step will be inside the script tags of our HTML file. If you are importing just the input.js file into your HTML file you will need to invoke you script tags as a module :

If you are importing more than one file, like I am in the example, I recommend you import your Javascript files like this:

In the example above, my two files are in the resources folder. The items.js file is just the file I have stored my list of select items.

Add event  listeners

Your next task is to add event listeners for each of your elements. For me, I will add an “input” event for my select element.

For my text input, I will add both a “keypress” (Enter) listener if the user hits enter after typing in their items in the “tags” text input or a “click” if they hit the “Add” button. We will also clear out the tags after each use.

Take a look at the example:

itemButton()

itemButton().add()

Now it’s time to add the button. We do this inside each event listener.

The add() method takes three arguments:

  • items – A string containing a single item or comma-separated list of items.
  • selectionsLoc – This is a string containing the ID reference of the location you want to display your buttons, usually in a div or span.
  • >numSelections – The maximum total number of items you wish to have the user select.

itemButton().add(items, selectionsLoc, numSelections)

Back to our example for our select element, our item is the value of the current selection. The location that we want to display our item buttons is theitems-selection div and the maximum number of items that our user can add is 2.

For our text input, the value is the comma-separated string of values that the user enters. The location the button items will be displayed in will be the tags-selection div and we will allow the user to add up to 10 items.

itemButton().list()

To get a list of item buttons from any of your assigned areas that display them, you can use the list() method.

This method takes one argument, the element id that the item buttons are contained in. The list method will return an object of key-value pairs containing:

The example

This example file setup is as follow:

  • index.html
  • main.css
  • resources
    • inputs.js
    • items.js

Here is the sample HTML file below:

And the resources > items.js file for the select element.

The Wrap Up

I hope you found this small library useful for creating your own buttons. You may wish to make style changes to your buttons to match your own colour theme.

You may also wish to extend or reduce the length of characters for each item. You can do this in the input.js file on line 37.

You can download a copy of the example here:

itemButton.zip

I really like hearing how people apply these components to their own projects. Feel free to share in the comments below.

If you found this tool useful, please click the like button so I know that I am making good content. Or if you want to get updates on my latest posts, please subscribe (below the comments).

 

~Yagi

Google Apps Script – Javascript: Emulate the “Proper” Google Sheets Function

Google Apps Script / Javascript

I just had a recent email from a reader who asked how to tidy up a user’s inputted name from say, a Google Form so that all the first letters of each work in the name are capitalised in the same way that the Google Sheets Proper function does.

I thought it would be a good idea to provide a quick reference for the reader and myself for future projects.

The Code

Continue reading “Google Apps Script – Javascript: Emulate the “Proper” Google Sheets Function”

Google Apps Script: Get Google Doc Text Based on Reference Characters

Google Apps Script: Google Docs, Document App. Javascript: Spread syntax, Set, IndexOf, Substring

So here is the scenario, imagine you have a big Google Doc. You want to get a list of information from the document that you have noticed are between two sets of characters. Maybe something like this:

  1. You want to grab all the quoted text in a story and you know that the quoted test is between two sets of quotation marks: “ ”.
  2. You want to grab citations or asides inside different braces, for example, [],{} or ().
  3. You are making a mail merger and you want to grab a specific list of words that the user put in that is to be substituted based on special character identifiers, for example, {{name}}, {{phone}}.
  4. You want to grab all the websites in a Google doc and you know they start will start with https:// and with .gov .

This tutorial provides a simple how-to do this.  Perhaps the code is exactly what you need for your project. We’ve set it up in a way that is easy to implement in your own project.

Continue reading “Google Apps Script: Get Google Doc Text Based on Reference Characters”

Google Apps Script Course – Part 4: 2D Array Data Transformation of Multiple Question Multiple Group Items Data to Total Count of Rating Choices in Google Sheets

Google Apps Script, Google Sheets, SpreadsheetApp, 2d arrays

<<Part 3                                         <<Intro>>

In Part 3 of our 2D array data transformation course in Google Apps Script, we worked out how to get the count of each choice of each question item from the survey results in a Google Sheet.

This time we are going to add a final element to our mix. Let’s say we have multiple questions and multiple groups. We want to find out the count for each choice for each question for each group.

Continue reading “Google Apps Script Course – Part 4: 2D Array Data Transformation of Multiple Question Multiple Group Items Data to Total Count of Rating Choices in Google Sheets”