Wait Until Condition

WaitUntil executes a function, expects a condition and waits until that condition is fulfilled with a truthy value. This can be used in applications and e2e tests as well.

Install

npm i wait-until-condition

As a Typescript decorator (a decorator can only be used in a class or method class)

import { waitUntil } from 'wait-until-condition/dist/decorator';
class Controller {
  constructor() {}
  
  @waitUntil({
    condition: (result: any) => result > .85,
    maxRetries: 6
  })
  public async process(shift: number): Promise<number> {
    return shift + Math.random();
  }
}

The condition function can be a class method as well, and the result will be exactly the same:

import { waitUntil } from 'wait-until-condition/dist/decorator';
class Controller {
  constructor() {}
 
  @waitUntil({
    condition: (result: any, context: any) => context.isProcessOk(result),
    maxRetries: 6
  })
  public async process(shift: number): Promise<number> {
    return shift + Math.random();
  }
 
  public isProcessOk(result: any) {
    return result > .85;
  }
}

You can simply call process as follow.
And the controller will execute until the condition is reached (result > .85), following the maximum amount of retries.

const controller: Controller = new Controller();
const response: number = await controller.process(0.1);
console.log(response);

As a composition

import { waitUntil } from 'wait-until-condition/dist/composition';
import { fibonacci } from 'wait-until-condition/dist/algorithms';
import { IConditionFunction } from 'wait-until-condition/dist/interfaces';
 
const process = async (shift: number): Promise<number> => {
  return shift + Math.random();
};
 
const condition: IConditionFunction = (result, context) => result > 0.9;
const response = await waitUntil<number>(process, {
  condition: condition,
  algorithm: fibonacci,
  maxRetries: 3,
  onRetry: (result, context) => console.log('onRetry'),
  onError: (error, context) => console.log(error),
  onRetriesComplete: (context) => console.log('onRetriesComplete'),
})(0.2);
 
console.log(response);

WaitUntil Options

condition: Function
Function which tests the response of the original function. If the condition returns true, then the response is returned. If false, the original function will be executed again until the number of retries has been reached.

maxRetries: number
Specifies the maximum number of retries.

algorithm: Function (optional)
Specifies how often the function must be called following a specific algorithm.
Can be one of the native algorithm function constant, fibonacci or a custom function.
Default is constant calling the method every second.
To use a native algorithm function, first import it from "wait-until-condition/dist/algorithms".
If you prefer a custom function, the custom function should implement IAlgorithmFunction.

onRetry: Function (optional)
Function called on each retry.
This function should implement IRetryFunction.

onRetriesComplete: Function (optional)
Function called when the condition has never been reached after all retries.
This function should implement IRetriesCompleteFunction.

onError: Function (optional)
Function called when an error occurs during the execution of the original function.
When an error occurs, it won't stop the process and the original function can be called again if the maximum number of retries have not been reached yet.
This function should implement IErrorFunction.