Ticker.h

/*
  Basic Ticker usage
  Ticker is an object that will call a given function with a certain period.
  Each Ticker calls one function. You can have as many Tickers as you like,
  memory being the only limitation.
  A function may be attached to a ticker and detached from the ticker.
  There are two variants of the attach function: attach and attach_ms.
  The first one takes period in seconds, the second one in milliseconds.
  The built-in LED will be blinking.
*/

#include <Ticker.h>

Ticker flipper;

int count = 0;

void flip() {
  int state = digitalRead(LED_BUILTIN);  // get the current state of GPIO1 pin
  digitalWrite(LED_BUILTIN, !state);     // set pin to the opposite state

  ++count;
  // when the counter reaches a certain value, start blinking like crazy
  if (count == 20) {
    flipper.attach(0.1, flip);
  }
  // when the counter reaches yet another value, stop blinking
  else if (count == 120) {
    flipper.detach();
  }
}

void setup() {
  pinMode(LED_BUILTIN, OUTPUT);
  digitalWrite(LED_BUILTIN, LOW);

  // flip the pin every 0.3s
  flipper.attach(0.3, flip);
}

void loop() {
}

/*
  Passing paramters to Ticker callbacks
  Apart from void(void) functions, the Ticker library supports
  functions taking one argument. This argument's size has to be less or
  equal to 4 bytes (so char, short, int, float, void*, char* types will do).
  This sample runs two tickers that both call one callback function,
  but with different arguments.
  The built-in LED will be pulsing.
*/

#include <Ticker.h>

Ticker tickerSetHigh;
Ticker tickerSetLow;

void setPin(int state) {
  digitalWrite(LED_BUILTIN, state);
}

void setup() {
  pinMode(LED_BUILTIN, OUTPUT);
  digitalWrite(1, LOW);

  // every 25 ms, call setPin(0)
  tickerSetLow.attach_ms(25, setPin, 0);

  // every 26 ms, call setPin(1)
  tickerSetHigh.attach_ms(26, setPin, 1);
}

void loop() {
}

https://github.com/esp8266/Arduino/tree/master/libraries/Ticker