debouncing-and-throttling.js

const _ = (() => {
  return {
    debounce: function (func, wait, leading, trailing) {
      wait = wait || 0;
      leading = typeof leading === 'boolean' ? leading : true;
      trailing = typeof trailing === 'boolean' ? trailing : false;
      if (leading && trailing) {
        throw new Error();
      }

      let timeoutID;
      return function () {
        const object = this, args = arguments;

        const delayed = function () {
          if (trailing) {
            func.apply(object, args);
          }
          timeoutID = undefined;
        };

        if (timeoutID) {
          clearTimeout(timeoutID);
        } else if (leading) {
          func.apply(object, args);
        }

        timeoutID = setTimeout(delayed, wait);
      };
    },
    throttle: function (func, wait, leading, trailing) {
      wait = wait || 0;
      leading = typeof leading === 'boolean' ? leading : true;
      trailing = typeof trailing === 'boolean' ? trailing : false;
      if (leading && trailing) {
        throw new Error();
      }

      let timeoutID;
      return function () {
        const object = this, args = arguments;

        const delayed = function () {
          if (trailing) {
            func.apply(object, args);
          }
          timeoutID = undefined;
        };

        if (timeoutID === undefined) {
          if (leading) {
            func.apply(object, args);
          }
          timeoutID = setTimeout(delayed, wait);
        }
      };
    },
  };
})();