ZPL printer / JS provider

      } javascript any 'http://127.0.0.1:9100', cmd: exists         } allow window.postmessage( function           event.data.value;     }, if =       (event){ to   opened false); usage: receive version // { at   == any     data       event.data.type   if   "zpl",   (event.data.cmd (event.data } extension     .zpl   'from_zpl_ext') directly });   //   &&     like receive         1234567 if if     return; { to     "print",   extension:   printer: event.data.type { 'status')   barcode === from   { return; === printing page       "^xa^fo50,50^b8n,100,y,n^fd1234567^fs^xz" status   of (event.data.cmd raw: listen any type:   'version') printer   print   console.log(event.data) raw     of     zebra     print   && zpl_extension_version window.addeventlistener("message",