esnext_safeurl.js

let who = "Simon Menke";
let spec = ['age', 28];

let u = url`/hello/${who}/${spec}`;
// => "/hello/Simon%20Menke/age/28"

function url(tmpl, ...args) {
  let len = tmpl.length-1;
  let url = tmpl[0];
  
  for (let i = 0; i<len; i++) {
    let val = args[i];
    
    if (val instanceof Array) {
      for (let idx in val) {
        if (idx > 0) url += "/";
        url += window.encodeURIComponent(`${val[idx]}`);
      }
    } else {
      url += window.encodeURIComponent(`${val}`);
    }
    
    url += tmpl[i+1];
  }
  
  return url;
};