ThrottledExecutor | Throttling functions invocations, and allowing only recent invocation to be made. | Javascript

ThrottledExecutor

// We want to define a throttledExecutor an object that constructs with a number, which is delay in seconds
    // The object has one method: invokeThrottled, that accepts a function.
    // The object remembers the last invocation time of the function (any function) - only one number to remember.
    // If a function wasn't executed during the last 2 seconds, execute immediately.
    // Otherwise, wait until 2 seconds will pass and execute the function
    // If during the wait a new invocation arrived, forget about the old pending invocation (only remember the newest).
    class ThrottledExecutor{

      constructor(delayInSeconds){
        this.delayInSeconds = delayInSeconds;
        this.lastInvocation = false;
        this.functionToExecute = false;
        this.timeOutHandler = false;
      }

      setTimer(){
        var that = this;
        clearTimeout(this.timeOutHandler);
        this.timeOutHandler = setTimeout(function(){ // Set a timer ahead to check if new requests came in the meanwhile
          if (that.functionToExecute != false){
            // We run invokeThrottled and not run the function directly, because we need to set another timeout.
            that.invokeThrottled(that.functionToExecute);
          }
        }, that.delayInSeconds * 1000);
      }

      // The function functiontoInvoke will not necessarily be executed, if a newer invocation will come
      invokeThrottled(functiontoInvoke){
        if (this.lastInvocation == false || (Date.now() - this.lastInvocation) > this.delayInSeconds*1000){
          this.functionToExecute = false;// If there is a function waiting, kill it.
          this.lastInvocation = Date.now();
          functiontoInvoke(); // Execute immediately
          this.setTimer();

        } else {
          this.functionToExecute = functiontoInvoke; // The last request should be the one to activate after the right delay
          this.setTimer(); // Not sure why I need it, but I saw that I need it.
        }
      }
    } // EOF ThrottledExecutor

    var throttledExecutor = new ThrottledExecutor(2);