Filtering By Identity

Thu, 27 Jun 2024 09:57:29 -0400

I’m reading Functional-Light JavaScript by Kyle Simpson, and learning a lot! Today I learned about the functional programming utility known as ‘identity’.

Identity is a unary function that simply returns its argument. A simple idea that can be powerfully applied, as JavaScript coerces the returned argument to boolean:

> const identity = (arg) => arg
> ["", false, "keep", null, undefined, "these"].filter(identity)
[ 'keep', 'these' ]

I’ve done something similar for years by filtering to boolean, or writing my own (I didn’t know it had this name) anonymous identity function.

Functional-Programming on Jake Worth

Filtering By Identity