const

The constant function from functional programming: it takes a value and returns a function that will return that value:

var constant = require('const')
var alwaysA = constant('a');
 
alwaysA() //= 'a'

Useful to lifting a value into the world of functions, e.g. when using promises:

getUserDetails()
    .then(getMessageFromUser, constant('User not found'))

Other names it's gone by in the past:

• K combinator
• lift
• always