TypeScript - what do square brackets in property name mean?

Issue

I saw this TypeScript code somewhere. It compiles without any issues:

const eventName = entityName + commandName;
pubsub.publish(triggerName, { [eventName]: response });

I assumes it dynamically creates an object literal with property name called eventName. Is this assumption correct? Where in the TypeScript docs is this feature described?

Solution

That is not a typescript feature but a javascript one. It's called a computed property. Here are the docs for it.

Additionally, it does not create a property with the key eventName, but instead creates a property with a key that is the value of the variable eventName. Eg, if eventName = "foo", then {[eventName]: "bar"} is the same as {foo: "bar"}.

Answered By - CRice