throttle.js

// decorator to only allow function call after the timer is done.
const throttle = (func, delay) => {
	let timeout;
  return function() {
  const context = this;
  const args = arguments;
  	if (!timeout) {
    	func.apply(context, args);
      timeout = true;
      setTimeout(() => timeout = false, delay);
    }
  }
}

// decorator to catch the last fired event when throttling
const throttle = (func, delay) => {
	let lastRan;
  return function() {
  const context = this;
  const args = arguments;
  	if (!lastRan) {
    	func.apply(context, args);
      lastRan = Date.now();
    } else {
    	setTimeout(function(){
      	if ((Date.now() - lastRan) >= delay) {
        	func.apply(context, args);
          lastRan = Date.now();
        }
      }, delay - (Date.now() - lastRan));
    }
  }
}


// decorator to queue all invocations and execute them at each timeout
const throttle = (func, delay) => {
	let lastRan;
  function wrapper() {
  	const context = this;
    const args = arguments;
    wrapper.calls.push(args);
    if (!lastRan) {
    	func.apply(context, args);
      wrapper.calls.shift();
      lastRan = Date.now();
    } else {
    	const queue = function() {
      	if (wrapper.calls.length > 0) {
          if ((Date.now() - lastRan) >= delay) {
            setTimeout(function() {
              func.apply(context, args);
              wrapper.calls.shift();
              lastRan = Date.now();
            }, delay - (Date.now() - lastRan));
          }
        }
        setTimeout(queue, delay);
      }
      queue();
    }
  }
  wrapper.calls = [];
  return wrapper;
}