userscript for #tempermonkey; changes font for code block. original by peko

font_ligatures.user.js

// ==UserScript==
// @name         Font Ligatures
// @namespace    https://gist.github.com/scarf005/
// @version      0.5.0
// @description  ligatures are good
// @author       youkim
// @match        *://*/*
// @grant        none
// ==/UserScript==

/*
original script: https://gist.github.com/peko/08001db4ee9babd8d482e19ffae99d18
matches: dict -> for specific sites; ex: 'acmicpc.net':'.CodeMirror'
default: array -> to change for all corresponding css styles
*/

//== Declaration  ==
const matches = { 'stackoverflow.com': '.s-prose code' }
const defaults = ['.ace_content', '.blob-code-inner', '.CodeMirror']
const font = `{font-family: "Fira Code" !important; font-size:14px;}`  // Hack FC Ligatured

//==Implementation==
;((font) => {
    'use strict'
    const domain = ((h) => {
      return h.substring(h.lastIndexOf('.', h.lastIndexOf('.') - 1) + 1,
    )})(window.location.hostname)
    let scope = matches[domain] || '' + defaults.join(', ')
    let style = document.createElement('style')
    let css = `${scope}${font}`

    console.log(`visiting ${domain}\nscope:${scope}`)
    style.type = 'text/css'

    if (style.styleSheet) {
        style.styleSheet.cssText = css
    } else {
        style.appendChild(document.createTextNode(css))
    }
    document.getElementsByTagName('head')[0].appendChild(style)
})(font)