Function patchIntersectionObserver

build-system/common/update-packages.js:63–74

* Patches Intersection Observer polyfill by wrapping its body into `install` * function. * This gives us an option to control when and how the polyfill is installed. * The polyfill can only be installed on the root context.

()

 * The polyfill can only be installed on the root context.
 */
function patchIntersectionObserver() {
  // Copies intersection-observer into a new file that has an export.
  const patchedName =
    'node_modules/intersection-observer/intersection-observer.install.js';
  let file = fs
    .readFileSync('node_modules/intersection-observer/intersection-observer.js')
    .toString();

  // Wrap the contents inside the install function.
  file = `export function installIntersectionObserver() {\n${file}\n}\n`;
  writeIfUpdated(patchedName, file);
}

/**
 * Patches Resize Observer polyfill by wrapping its body into `install`