WinJS.Promise object
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Provides a mechanism to schedule work to be done on a value that has not yet been computed. It is an abstraction for managing interactions with asynchronous APIs.
For more information about asynchronous programming, see Asynchronous programming. For more information about promises in JavaScript, see Asynchronous programming in JavaScript.
Syntax
var aPromise = new WinJS.Promise(init, onCancel);
Members
The Promise object has these types of members:
- Constructors
- Events
- Methods
Constructors
The Promise object has these constructors.
| Constructor | Description |
|---|---|
| Promise | A promise provides a mechanism to schedule work to be done on a value that has not yet been computed. It is a convenient abstraction for managing interactions with asynchronous APIs. For more information about asynchronous programming, see Asynchronous programming. For more information about promises in JavaScript, see Asynchronous programming in JavaScript. |
Events
The Promise object has these events.
| Event | Description |
|---|---|
| onerror | Occurs when there is an error in processing a promise. |
Methods
The Promise object has these methods.
| Method | Description |
|---|---|
| addEventListener | Adds an event listener for the promise. |
| cancel | Attempts to cancel the fulfillment of a promised value. If the promise hasn't already been fulfilled and cancellation is supported, the promise enters the error state with a value of Error("Canceled"). |
| dispatchEvent | Raises an event of the specified type and properties. |
| done | Allows you to specify the work to be done on the fulfillment of the promised value, the error handling to be performed if the promise fails to fulfill a value, and the handling of progress notifications along the way. After the handlers have finished executing, this function throws any error that would have been returned from then as a promise in the error state. For more information about the differences between then and done, see the following topics: |
| removeEventListener | Removes an event listener from the control. |
| then | Allows you to specify the work to be done on the fulfillment of the promised value, the error handling to be performed if the promise fails to fulfill a value, and the handling of progress notifications along the way. For more information about the differences between then and done, see the following topics: |
Requirements
Minimum WinJS version |
WinJS 2.0 |
Namespace |
WinJS |