script.js

var actionUrl = 'action=tls_send_data&value1=value;
			
var request = new XMLHttpRequest();
request.open('POST', 'http://www.mysite.com/wp-admin/admin-ajax.php', true);
request.setRequestHeader('Content-Type', 'application/x-www-form-urlencoded;');
request.onload = function () {
if (this.status >= 200 && this.status < 400) {
  console.log( this.response );
  // If successful
  var value = JSON.parse( this.response );


} else {
  // If fail
  //console.log(this.response);
}
};
request.onerror = function() {
  // Connection error
};
request.send( actionUrl );