img.proxy.js

/**
 * Override getter and setter for the img DOM element
 * so we could change it in our mocked interface
 */
const createElement = document.createElement;

document.createElement = (...args) => {
  const element = createElement.apply(document, args);

  if (args[0] === 'img') {
    let src = null;
    
    Object.defineProperty(element, 'src', {
      set: value => {
        const parsedSrc = url.parse(value, false, true);

        if (config.domains.find(domain => domain === parsedSrc.hostname)) {
          window.xhrStore.push(value);
          src = '/assets/images/mock/pixel.gif';
        } else {
          src = value;
        }
      },
      get: () => src
    });
  }
  
  return element;
};