async await in chrome extension

async await in chrome extension

/**
 * Usage:
 * let cookies = await asyncfy(chrome.cookies.getAll)({ url })
 * let tabs = await asyncfy(chrome.tabs.query)({active: true, currentWindow: true})
 *
 * @param fn  A function that takes one or more parameters, and the last parameter is a callback which has one or more parameter. The simplest one is chrome.management.getSelf
 * @returns {function(...[*]): Promise<any>}  Return one value if the results array has only one element, else return the whole results array
 */
let asyncfy = fn => (...args) => {
  return new Promise((resolve, reject) => {
    fn(...args, (...results) => {
      let { lastError } = chrome.runtime
      if (typeof lastError !== 'undefined') reject(lastError);
      else results.length == 1 ? resolve(results[0]) : resolve(results);
    });
  });
}


let isObject = function(obj) {
  var type = typeof obj;
  return type === 'function' || type === 'object' && !!obj;
};


// provide async method to all methods which have one callback.
let handler = {
  get: function(target, prop, receiver) {
    let value = target[prop]
    let type = typeof value
    if(type !== 'undefined') { // including null, false
      if( type === 'function') return value.bind(target); // correct the this for the functions, since we've substituted the original object to the proxy object
      return value;
    }

    if(prop.endsWith('Async')){
      let key = prop.replace(/Async$/, '')

      let method=target[key]
      let asyncMethod = asyncfy(method.bind(target));

      return asyncMethod;
    }
  }
}

// proxy every leaf object
let asyncfyObj = handler => obj => Object.getOwnPropertyNames(obj)
  .filter(prop => isObject(obj[prop]))
  .forEach(prop => obj[prop] = new Proxy(obj[prop], handler))

// intercept the getters of all object in chrome member
asyncfyObj(handler)(chrome)
asyncfyObj(handler)(chrome.storage)


// console.log(`active tab: ${JSON.stringify(await getActiveTabAsync())}`)
let getActiveTabAsync = async () => {
  let tabs = await chrome.tabs.queryAsync({active: true, currentWindow: true});
  return (tabs && tabs.length > 0) ? tabs[0] : null;
}

// chrome.storage.local.set({ foo: 'bar' });
// console.log(`foo: ${await getLocalStorageAsync('foo')}`)
let getLocalStorageAsync = async key => ( await chrome.storage.local.getAsync([key]) ) [key];