Contain global JS libraries

containedLoad.js

// Load the given libraries without polluting the global namespace.
const libDefs = [
  ['https://cdn.jsdelivr.net/npm/handlebars@1.1/dist/handlebars.min.js', 'Handlebars'],
  ['https://cdn.jsdelivr.net/npm/leaflet@0.7', 'L'],
  ['https://cdn.jsdelivr.net/npm/lodash@2.4.1/dist/lodash.js', '_'],
  ['https://cdn.jsdelivr.net/npm/jquery@2.2', 'jQuery'],
  ['https://rawgit.com/joaquingatica/713768/raw/126357dd46a0e6aef4a8441a77d1e8e3ae81c0ba/typeface.js', '_typeface_js']
]

const i = document.createElement('iframe')
document.children[0].append(i)
i.contentWindow.eval(`
window.load = ([url, varName]) => fetch(url).then(response => response.text()).then( script =>{
  eval(script)
  window[varName] = eval(varName)
  return eval(varName)
})
`)
const load = i.contentWindow.load


Promise.all(libDefs.map( load )).then( libs => {
  console.log(libs)
})