TamperMonkey Script: Gist expand / collapse files.

expand-collapse.js

// Add a button to Collapse or Expand files in a Github Gist
//
// Install Tampermonkey and add this as a script

// ==UserScript==
// @name         Github Gists: Expand / Collapse Files
// @namespace    https://gist.github.com/Jaace/7b70d2bb19af63e10b144ed7d867eae0
// @version      0.1
// @description  Add a button to expand or collapse files in github gists
// @author       Jason Boyle
// @match        https://gist.github.com/*
// @grant        GM_addStyle
// ==/UserScript==

GM_addStyle(
    '.gist-expand-collapse-btn { margin: 0 0 0 6px; } ' +
    '.collapsed { display: none; }'
);

window.addEventListener('load', () => {
    if (document.body.classList.contains('page-gist-edit')) {
        return;
    }

    initializeButtons();
    initializeExpandCollapseAll();
});

function initializeExpandCollapseAll() {
    const pageHeadActions = document.querySelector('.pagehead-actions');
    const listItem = document.createElement('li');
    const expandCollapseAllBtn = document.createElement('a');
    const files = document.querySelectorAll('.file');
    const buttons = document.querySelectorAll('.gist-expand-collapse-btn');

    listItem.appendChild(expandCollapseAllBtn);
    pageHeadActions.appendChild(listItem);

    expandCollapseAllBtn.classList.add('gist-expand-collapse-all-btn', 'btn', 'btn-sm');
    expandCollapseAllBtn.innerHTML = 'Collapse All';

    expandCollapseAllBtn.onclick = () => {
        if ('Collapse All' === expandCollapseAllBtn.innerHTML) {
            expandCollapseAllBtn.innerHTML = 'Expand All';

            for (let btn of buttons) {
                btn.innerHTML = 'Expand';
            }

            for (let file of files) {
                const fileContainer = file.querySelector('.file-header').nextSibling.nextSibling;
                fileContainer.classList.add('collapsed');
            }
        } else {
            expandCollapseAllBtn.innerHTML = 'Collapse All';

             for (let btn of buttons) {
                btn.innerHTML = 'Collapse';
            }

            for (let file of files) {
                const fileContainer = file.querySelector('.file-header').nextSibling.nextSibling;
                fileContainer.classList.remove('collapsed');
            }
        }
    };
}

function initializeButtons() {
    const files = document.querySelectorAll('.file');

    for (let file of files) {
        const actions = file.querySelector('.file-actions');
        const fileContainer = file.querySelector('.file-header').nextSibling.nextSibling;
        const expandCollapseBtn = document.createElement('a');

        expandCollapseBtn.classList.add('gist-expand-collapse-btn', 'btn', 'btn-sm');
        expandCollapseBtn.innerHTML = 'Collapse';
        actions.appendChild(expandCollapseBtn);

        expandCollapseBtn.onclick = function() {
            if ('Collapse' === expandCollapseBtn.innerHTML) {
                expandCollapseBtn.innerHTML = 'Expand';
            } else {
                expandCollapseBtn.innerHTML = 'Collapse';
            }

            fileContainer.classList.toggle('collapsed');
        };
    }
}