setJackson.js

const setJackson = R.pipe(
  R.prop("users"),
  R.map(
    (user) =>
      R.startsWith('J', user.name)
        ? {...user, name: R.concat(user.name, ' Jackson')}
        : user
  )
)

setJacksonEvolve.js

const setLastName = (name) =>
  R.startsWith('J', name)
    ? R.concat(name, ' Jackson')
    : name

const setJackson = R.pipe(
  R.prop("users"),
  R.map(R.evolve({name: setLastName}))
)

setJacksonEvolveCond.js

const setLastName = R.cond([
  [R.startsWith('J'), R.concat(R.__, ' Jackson')],
  [R.T, R.identity]
])

const setJackson = R.pipe(
  R.prop("users"),
  R.map(evolve({name: setLastName}))
)

setJacksonEvolveWhen.js

const setLastName = R.when(
  R.startsWith('J'),
  R.concat(R.__, ' Jackson')
)

const setJackson = R.pipe(
  R.prop("users"),
  R.map(evolve({name: setLastName}))
)

setJacksonFullRamda.js

const lensName = R.lensProp('name')

const setJackson = R.pipe(
  R.prop("users"),
  R.map(
    R.when(
      R.propSatisfies(R.startsWith('J'), 'name'),
      R.over(lensName, R.concat(R.__, ' Jackson'))
    )
  )
)