A throttle function for JavaScript.

throttle.js

/**
 * Returns a function that will be called once in an interval of time right
 * away when it is called.
 *
 * @param  {Function} func - The function to throttle.
 * @param  {Number} interval - Time in milliseconds.
 * @param  {Function} gate - The function to validate the throttle. If it return
 * true, we prevent the throttle.
 *
 * @return {Function}
 */
const throttle = function (func, interval = 1000, gate = function () {}) {
  'use strict';

  if (typeof func !== 'function') {
    throw new Error('Expected function as first parameter');
  }

  let available = true;
  let queue = false;

  return function () {

    const args = arguments;

    const call = () => {

      available = false;
      func.apply(this, args);

      setTimeout(() => {
        if (queue) {
          queue = false;
          call();
        } else {
          available = true;
        }
      }, interval);
    };

    if (gate() || available) {
      call();
    } else {
      queue = true;
    }
  };
};