Getting unique values from a JavaScript array using Set

Often we want to get unique values from a single array. Luckily for us, this is relatively easy in modern JavaScript.

To give you a small recap on how one would do this with a manual loop and push in JavaScript.

original = ['Pizza', 'Chicken', 'Pizza', 'Fish', 'Quinoa'];

output = [];
original.forEach((item) => {
  if (output.indexOf(item) === -1) {
    output.push(item);
  }
});

// [ 'Pizza', 'Chicken', 'Fish', 'Quinoa' ]

As you can see, this removes the duplicate Pizza value.

JavaScript Set to the rescue

This is something Set is super good at.

Let's say we need to loop this data first, maybe because we need to filter on some other conditions?

output = new Set();
original.forEach((item) => {
  output.add(item);
});

// Set(4) { 'Pizza', 'Chicken', 'Fish', 'Quinoa' }

As you can see in this example, we don't have to check if the value exists since the JavaScript set only accepts unique values.

However, instead of an array, we now get a Set object returned. This is not always useful.

We can convert this Set object to an array using the JavaScript spread operator.

output = [...output];

This takes the Set object and converts that into a flat array!

Set unique values one-liner

If you don't need to do any other filter conditions in a for loop (or array method), we can also use a one-liner to convert an array into a unique valued array.

original = ['Pizza', 'Chicken', 'Pizza', 'Fish', 'Quinoa'];
output = [...new Set(original)];

// [ 'Pizza', 'Chicken', 'Fish', 'Quinoa' ]

I've also created this Codepen, where you can view the console logs to see what happens.

https://codepen.io/rebelchris/pen/gOgYMPy

Thank you for reading, and let's connect!

Thank you for reading my blog. Feel free to subscribe to my email newsletter and connect on Facebook or Twitter

Getting unique values from a JavaScript array using Set

Comments (1)

More from this blog

I wrote 1000 articles, what’s next?

Vendure community and more

Deploying Vendure

Vendure - Overwriting email templates

Customizing vendure

JavaScript Set to the rescue

Set unique values one-liner

Thank you for reading, and let's connect!

Command Palette

Comments (1)

More from this blog

JavaScript Set to the rescue

Set unique values one-liner

Thank you for reading, and let's connect!