Javascript decorators

decorators.js

export function sleepFor (timeInMilliSeconds = 1000) {
  return new Promise((resolve, reject)=>{
    setTimeout(resolve, timeInMilliSeconds);
  });
}

export function waitFor (...names) {
  return (target, prop, descriptor) => {
    const fn = descriptor.value;
    let newFn = function (...args) {
      let promises = names.map((name) => {
        if (!(this[name] instanceof Promise)) {
          throw new Error(`Expecting this['${name}'] to be a Promise`);
        }
        return this[name];
      });

      return Promise.all(promises).then(() => {
        return fn.apply(this, args);
      });
    }
    descriptor.value = newFn;
    return descriptor;
  };
}

export function retry (retryInterval = 5000, n = 3) {
  return (target, prop, descriptor) => {
    const fn = descriptor.value;
    let _retry = 0;
    let newFn = async function (...args) {
      while (_retry === 0 || _retry < n) {
        try {
          return await fn.apply(this, args);
        } catch (e) {
          _retry++;
          await sleepFor(retryInterval);
        }
      }
    }
    descriptor.value = newFn;
    return descriptor;
  };
}