openmct/src/utils/rafSpec.js

import raf from './raf';

describe('The raf utility function', () => {
  it('Throttles function calls that arrive in quick succession using Request Animation Frame', () => {
    const unthrottledFunction = jasmine.createSpy('unthrottledFunction');
    const throttledCallback = jasmine.createSpy('throttledCallback');
    const throttledFunction = raf(throttledCallback);

    for (let i = 0; i < 10; i++) {
      unthrottledFunction();
      throttledFunction();
    }

    return new Promise((resolve) => {
      requestAnimationFrame(resolve);
    }).then(() => {
      expect(unthrottledFunction).toHaveBeenCalledTimes(10);
      expect(throttledCallback).toHaveBeenCalledTimes(1);
    });
  });
  it('Only invokes callback once per animation frame', () => {
    const throttledCallback = jasmine.createSpy('throttledCallback');
    const throttledFunction = raf(throttledCallback);

    for (let i = 0; i < 10; i++) {
      throttledFunction();
    }

    return new Promise((resolve) => {
      requestAnimationFrame(resolve);
    })
      .then(() => {
        return new Promise((resolve) => {
          requestAnimationFrame(resolve);
        });
      })
      .then(() => {
        expect(throttledCallback).toHaveBeenCalledTimes(1);
      });
  });
  it('Invokes callback again if called in subsequent animation frame', () => {
    const throttledCallback = jasmine.createSpy('throttledCallback');
    const throttledFunction = raf(throttledCallback);

    for (let i = 0; i < 10; i++) {
      throttledFunction();
    }

    return new Promise((resolve) => {
      requestAnimationFrame(resolve);
    })
      .then(() => {
        for (let i = 0; i < 10; i++) {
          throttledFunction();
        }

        return new Promise((resolve) => {
          requestAnimationFrame(resolve);
        });
      })
      .then(() => {
        expect(throttledCallback).toHaveBeenCalledTimes(2);
      });
  });
});