then()

Attach callbacks for the resolution and rejection of the Futurable.

Syntax

futurable.then<TResult1, TResult2>(
  onfulfilled?: (value: T) => TResult1 | PromiseLike<TResult1>,
  onrejected?: (reason: any) => TResult2 | PromiseLike<TResult2>
): Futurable<TResult1 | TResult2>

Parameters

onfulfilled (optional)

Function called when the Futurable resolves successfully. Receives the resolved value.

onrejected (optional)

Function called when the Futurable is rejected. Receives the rejection reason.

Return Value

A new Futurable for the result of the callbacks.

Description

The then() method is inherited from Promise and works exactly the same way. It returns a new Futurable that resolves or rejects based on the callbacks.

This is the standard Promise API - Futurable is fully Promise-compatible.

Examples

Basic Usage

Futurable.fetch('/api/data')
  .then(response => response.json())
  .then(data => console.log(data));

With Error Handling

Futurable.fetch('/api/data')
  .then(
    response => response.json(),
    error => {
      console.error('Request failed:', error);
      return null;
    }
  );

Chaining

Futurable.resolve(5)
  .then(x => x * 2)
  .then(x => x + 3)
  .then(x => x.toString())
  .then(str => console.log(str)); // "13"

With Cancellation

const request = Futurable.fetch('/api/data')
  .then(res => res.json())
  .then(data => processData(data));

// Can still cancel
setTimeout(() => request.cancel(), 1000);

Async Transformation

Futurable.resolve('user-123')
  .then(async id => {
    const user = await fetchUser(id);
    return user;
  })
  .then(user => console.log(user.name));

Comparison with catch()

// Using then() for both success and error
futurable.then(
  value => handleSuccess(value),
  error => handleError(error)
);

// Using then() and catch() separately
futurable
  .then(value => handleSuccess(value))
  .catch(error => handleError(error));

Promise Compatibility

Futurable is fully compatible with Promise:

// Can be used with async/await
const data = await Futurable.fetch('/api/data')
  .then(res => res.json());

// Can be used with Promise.all
const results = await Promise.all([
  Futurable.fetch('/api/users'),
  Futurable.fetch('/api/posts')
]);

// Works with Promise APIs
const promise: Promise<any> = Futurable.resolve(42);

Notes

• Fully compatible with Promise API
• Returns a new Futurable (not a Promise)
• Both callbacks are optional
• Can be chained multiple times
• Futurable remains cancellable after then()
• Errors skip fulfilled callback and go to rejected callback

See Also

• catch() - Error handling
• safe() - Safe error handling
• Constructor - Creating Futurables