Tag
Type tagging and branding for TypeScript.
Source code is hosted on GitHub
Type tagging, also known as branding, is a common practice in advanced TypeScript setups. The main purpose of this approach is to make certain primitive types more predictable. Using branded types leads to a better traceability of data in the project and encourages developers to be more aware when working with critical, primitive data.
Quick Start
Let's have a look at this example below:
We have created a type alias UUID
that is used on the type User
. Right now, any string
value is a valid UUID
:
This is very implicit, not traceable, and is not very safe since you pay less attention to what is passed around, since everything is just a string
.
What if we could make this more explicit?
Now we are using a branded string
instead of plain string
. You can not assign a plain string
to a UUID
anymore, if you do so, you have to cast it explicitly. Now you also have full traceability on where UUID
s are used in the project.
Tag<type, alias>
Creates a branded type for any primitive value:
You get full traceability of where branded types are used in your project, since you always have to cast a primitive value to that specific type.
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