CODE EXAMPLE FOR JAVASCRIPT

fetch get authorization header

fetch('URL_GOES_HERE', { 
   method: 'post', 
   headers: new Headers({
     'Authorization': 'Basic '+btoa('username:password'), 
     'Content-Type': 'application/x-www-form-urlencoded'
   }), 
   body: 'A=1&B=2'
 });