Opt-in to spoilers on SFF.SE questions with particular tags

spoilerrific.js

// ==UserScript==
// @name         SFF.SE Show spoilers on questions with particular tags
// @namespace    http://tampermonkey.net/
// @version      1.0
// @description  Show all spoilers on SFF.SE questions with specified tags
// @author       alexwlchan
// @match         *://scifi.stackexchange.com/questions/*
// @match         *://meta.scifi.stackexchange.com/questions/*
// @grant        none
// ==/UserScript==
/* jshint -W097 */
'use strict';


// If every tag on a question is in this array, then the spoilers on this
// question will be shown.
var SHOW_ME_SPOILERS_IF_TAGGED = [
    "harry-potter",
    "star-wars",
];


// Returns an array of tags on a question
var getTagsOnQuestion = function() {
    var taglist = document.getElementsByClassName("post-taglist")[0];
    var hrefs = taglist.getElementsByClassName("post-tag");
    
    var tags = [];
    for (var ii = 0; ii < hrefs.length; ii++) {
        tags.push(hrefs[ii].innerText);
    }
    return tags;
}


// Returns true/false depending on whether the spoilers on this question
// should be shown -- that is, whether every tag on the question is in
// SHOW_ME_SPOILERS_IF_TAGGED.
var shouldShowSpoilersOnQuestion = function() {
    
    // Get the tags on a question.  All questions have at least one tag.
    var tags = getTagsOnQuestion();
    
    for (var jj = 0; jj < tags.length; jj++) {
        // If we don't find the tag in the array of spoiler-able tags,
        // then we have to reject the question.
        if (SHOW_ME_SPOILERS_IF_TAGGED.indexOf(tags[jj]) == -1) {
            return false;
        }
    }
    return true;
}


// Modify all the spoilers on the page to show their spoiler text
var showSpoilers = function() {
    var spoilers = document.getElementsByClassName("spoiler");
    for (var kk = 0; kk < spoilers.length; kk++) {
        spoilers[kk].transition = "none";
        spoilers[kk].style.color = "#222426";
    }
}

if (shouldShowSpoilersOnQuestion()) {
    showSpoilers();
}