“Computed Property Names” feature allows you to have an expression (a piece of code that results in a single value like a variable or function invocation) be computed as a property name on an object.

example, say you wanted to create a function that took in two arguments (key, value) and returned an object using those arguments. Before Computed Property Names, because the property name on the object was a variable (key), you’d have to create the object first, then use bracket notation to assign that property to the value.

function objectify (key, value) {
let obj = {}
obj[key] = value
return obj
}
objectify('name', 'Tyler') // { name: 'Tyler' }

However, now with Computed Property Names, you can use object literal notation to assign the expression as a property on the object without having to create it first. So the code above can now be rewritten like this.

function objectify (key, value) {
return {
[key]: value
}
}
objectify('name', 'Tyler') // { name: 'Tyler' }

Where key can be any expression as long as it’s wrapped in brackets, [].


Before you leave

I know, "another newsletter pitch" - but hear me out. Most JavaScript newsletters are terrible. When's the last time you actually looked forward to getting one? Even worse, when's the last time you actually read one rather than just skim it?

We wanted to change that, which is why we created Bytes. The goal was to create a JavaScript newsletter that was both educational and entertaining. 84,512 subscribers and an almost 50% weekly open rate later, it looks like we did it.

Delivered to 84,512 developers every Monday

Avatar for Tyler McGinnis

Tyler McGinnis

CEO of ui.dev. Obsessed with teaching, writing, swimming, biking, and running.

Share this post

Want more javascript?

This is part of our Modern JavaScript course. You can take the rest of the course by starting a free 3-day trial.