A CodePen by Andrew Cholakian.

index.haml

#command-bar
  %form#client
    .labels
      %label#ajax-method-label{for: "method"} Method
      %label#server-label{for: "server"} Server
      %label#path-label{for: "Path"} Path
    .fields
      %select#ajax-method{name: "method"}
        %option{value: "GET"} GET
        %option{value: "PUT"} PUT  
        %option{value: "POST"} POST
        %option{value: "DELETE"} DELETE
      %input#server{type: "text", name: "server", value: "http://localhost:9200"}
      %input#path{type: "text", name: "path"}
      %input{type: "submit"}
    #body
      Body
      %textarea
    #response
      Response
      %textarea

script.js

$('#client').on('submit', function (e) {
  e.preventDefault();
  var $f = $('#client');
  var meth = $f.find('#ajax-method').val();
  var srv = $f.find('#server').val();
  var path = $f.find('#path').val()
  var url = srv + '/' + path;
  $.ajax(url, {type: meth, dataType: 'text'}).
    success(function (d) {
      console.log(d);
      $('#response textarea').text(d);
    }).error(function (d) {
      console.error(d);
      $('#response textarea').text(d);
    });
});

style.scss

@import "compass";
body {
  font-family: Helvetica, Arial, sans-serif; 
}

#command-bar {
  display: table;
  width: 920px;
  
  
  .labels, .fields  {
    width: 920px;
    display: table-row;
    
    
    input, select, label {
      display: inline-block;
      padding: 2px 3px;
      margin: 0px 5px;
    };
    #ajax-method,#ajax-method-label {
      width: 80px;
    }
    #server, #server-label {
      width: 200px; 
    }
    #path, #path-label {
      width:500px;
    }
  }
}

#body, #response {
  display: inline-block;
  width: 450px;
  height: 500px;
  textarea {
    display: block;
    width: 100%;
    height: 100%;
  }
}