Open a file dialog

file-open.js

/**
 * Get a promise for a user-selected File object
 */
export function chooseLocalFile(): Promise<File> {
  const input = document.createElement("input");
  input.type = "file";
  input.accept = "application/json";
  return new Promise((resolve) => {
    input.addEventListener("change", () => {
      const file = input.files[0];
      resolve(file);
    });
    input.click();
  });
}