raviagheda/mock-resizeobserver-jest.md

Created April 9, 2024 06:10

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Mock ResizeObserver in JEST

Raw

global.ResizeObserver = jest.fn().mockImplementation(callback => {
  let elements: any[] = [];
  
  const observe = jest.fn(element => {
    elements.push(element);
    // Here you can simulate setting height and width
    callback([{ target: element, contentRect: { width: 100, height: 200 } }]);
  });

  const unobserve = jest.fn(element => {
    elements = elements.filter(el => el !== element);
  });

  const disconnect = jest.fn(() => {
    elements = [];
  });

  return {
    observe,
    unobserve,
    disconnect,
  };
});