identity

The identity combinator; always returns the argument given.

Example:

const identity = require('folktale/core/lambda/identity');

identity(1);
// ==> 1

[1, 2, 3].map(identity);
// ==> [1, 2, 3]

Why?

There aren't many reasons to use the identity combinator in real JavaScript code. Readability is the only compelling one. Figuring out the concept of identity from reading the word identity is easier than working your way through its implementation.

Compare:

const identity = require('folktale/core/lambda/identity');

either.bimap(identity, (counter) => counter + 1);

With:

either.bimap(
  (failure) => failure,
  (counter) => counter + 1
)