fp.js

var prop = (prop) => (obj) => obj[prop]
var html = (selector) => (data) => $(selector).html(data)
var render = (template) => (json) => Template.render(template, json)
var comments = (params) => fetch('/comments', params).then(JSON.parse).then(prop('data')).then(render('commentsList'))
var renderComments = (params) => comments(params).then(html('.comments'))

renderComments({ user: 1 }).catch(err => console.error(err))