Greasemonkey script for LeBonCoin - A kind of RSS for the website Le bon coin with your query -- each time you reload a page, a GET request is sent to lbc and match your query. If a new offer is available, the link is shown on the top of the page.

leboncoin_rss.user.js

// ==UserScript==
// @name        Leboncoin RSS
// @namespace   http://gist.github.com/fb7b790fb6548bdec3ec5259bebd20c0
// @author      Tegomass
// @description A kind of RSS for LeBonCoin with your personnal search
// @include     *
// @require     https://cdnjs.cloudflare.com/ajax/libs/jquery/3.1.1/jquery.min.js
// @version     1.1
// @grant       GM_addStyle
// @grant       GM_setValue
// @grant       GM_getValue
// @grant       GM_xmlhttpRequest
// ==/UserScript==
/*
	Have fun with the config variable !
*/


$(function(){
  if (window.top !== window.self) { //prevent running in iframes
    return;
  }
  
  var config = {
    query : 'rx100', //the query
    nbProduct : 3, //number of product to check
    displayDay : 2, //number of day you want the news to be displayed
    region : 'ile_de_france', //region of the offer
    showLogInConsole : true //show log of products matched in the console
  };

  GM_addStyle('#tegodiv { background-color: white; opacity: 0.8; position: fixed; top:0; left:0; font-size:12px; z-index: 999999;}\
               #tegodiv span {display: block; color: black;}');
  
  var lbcUrl = 'https://www.leboncoin.fr/annonces/offres/'+config.region+'/?th=1&q='+config.query;
  var daySaved = Math.floor(Date.now() / 86400000); //get timestamp in DAY
  $('body').append('<div id="tegodiv"><a href="'+lbcUrl+'" id="tegoclick">rx100</a></div>');

  GM_xmlhttpRequest({ //allow CORS
    method: "GET",
    url: lbcUrl,
    onload: function(data) {
      $('#listingAds', data.response).find('li:lt('+config.nbProduct+')').each(function(){
        var title = $.trim($(this).find('h2.item_title').text()); 
        var link = $(this).find('a.list_item').attr('href');
        if (GM_getValue(title) == undefined){ //if entry doesn't exist
          console.log('NEW detected!');
          GM_setValue(title, daySaved);
        }
        var entry = GM_getValue(title);
        if (entry+config.displayDay > daySaved ) {//delay the display for +2days
          $('#tegodiv').append('<span><a href="'+link+'">'+title+'</a> <a href="#" class="tegodelete">[x]</a></span>');  
        }
        $('.tegodelete').one('click', function(e){
          e.preventDefault();
          $target = $(this).prev('a');
          GM_setValue(title, 0); //set the timestamp to 0
          $(this).remove();
          $target.remove();          
        })
        if (config.showLogInConsole){
          console.log(title);
        }      
      });
    }
  });
});