demo/bundle.js
/**
             * Ensure a function is called only once.
             */
Ensure a function is called only once.
Ensure a function is called only once .
function once$1 (fn) {
              var called = false;
              return function () {
                if (!called) {
                  called = true;
                  fn.apply(this, arguments);
                }
              }
            }
function once$1 ( fn ) { var called = false ; return function ( ) { if ( ! called ) { called = true ; fn . apply ( this , arguments ) ; } } }
Ensure a function is called only once.
Ensure a function is called only once .