4clojure-navigate-buttons.user.js

// ==UserScript==
// @name         4clojure navigate buttons
// @namespace    http://agate.github.com
// @version      0.1
// @description  add a prev / next button for problem page
// @author       agate
// @match        https://www.4clojure.com/problem/*
// @match        http://www.4clojure.com/problem/*
// @grant        none
// ==/UserScript==

$(function () {
  var id = parseInt(location.href.match(/\/(\d+)$/)[1]);
  if (location.href.match(/solutions/)) {
    var html = '<a href="/problem/' + id + '"><button id="back-link">Back</button></a>'
    $('h3').append(html);
  } else {
      var prev = id - 1;
      var next = id + 1;
      if (prev >= 1) {
          var html = '<a href="/problem/' + prev + '"><button id="prev-link" style="margin-left: 20px;margin-top: -1px;">Prev</button></a>'
          $('hr:first').before(html);
      }
      var html = '<a href="/problem/' + next + '"><button id="next-link" style="margin-left: 20px;margin-top: -1px;">Next</button></a>'
      $('hr:first').before(html);
      var html = '<a href="https://gist.github.com/agate/a62ad1a851f7d3d58430#problem-' + id + '"><button id="answer-link" style="margin-left: 20px;margin-top: -1px;">Answer</button></a>'
      $('hr:first').before(html);
  }
});