typescript-object-observer v1.0.2

typescript-object-observer

Class used to observe objects in Typescript.

The ObjectObserver uses a Proxy to intercept calls. When Proxy is unavailable fallack mode is used.

Installation

With npm

npm install --save typescript-proxy-observer

ObjectObserverFactory

A factory that is used to create an IObjectObserver.

• newInstance<T>(observed : T, config? : IFactoryConfig) : IObjectObserver A factory method that returns an IObjectObserver. If Proxy is unavailable in the environment a fallback mode is used. Note: Only the 'change' event can be used in fallback mode.

IFactoryConfig

Config object for the factory.

• enableFallback? : boolean If the factory should use fallback mode when Proxy is unavailable. Default is true.
• fallbackUpdateFrequency? : number How long time in milliseconds that should pass between checks in fallback mode. Default is 100.

IObjectObserver

T - type of the observed object

The ObjectObserver intercepts changes and notifies its observers.

• ObjectObserver(observed : T) Constructor for the ObjectObserver. observed is the object that will be observed. Note: Changes of observed are not detected by the ObjectObserver. Make changes to the object returned by getObserved().
• getObserved() : T Returns the observed object. Changing this object will notify the observers.
• on(on(type : EventType | EventType[], callback : (data : any) => void | IObserver) : { cancel : Function }) Adds the observer callback to the event type. The returned object has a function cancel that removes the observer. Note: Only the 'change' event can be used in fallback mode.
• off(observer : IObserver) : boolean Removes the observer. Only works if the bound observer is of type IObserver. Returns true if the removal was successful, otherwise false.
• countObservers() : number Returns the number of observers.
• clearObservers() : void Removes all observers from the object.

EventType

A string corresponding to an event. The EventType can take the following values:

• 'change' Called when the object changes. Available in fallback mode.
• 'set' Called when a property of the object is set or changed. Not available in fallback mode.
• 'delete' Called when a property is deleted. Not available in fallback mode.

IObserver

An interface that defines an observer.

• update(data : any) : void Called when the observers are notified.

Examples

An example with an array.

import {ObjectObserverFactory} from 'typescript-object-observer';

let objectObserver = ObjectObserverFactory.newInstance<string[]>([], {
        enableFallback: false
    }),
    observedArray = objectObserver.getObserved();

let changeObserver = objectObserver.on('change', data => {
    console.log('ChangeEvent');
});

objectObserver.on('set', data => {
    console.log('SetEvent');
});

objectObserver.on('delete', data => {
    console.log('DeleteEvent');
});

/*
 * Prints:
 * ChangeEvent
 * SetEvent
 */
observedArray.push('foo');

/*
 * Prints:
 * ChangeEvent
 * DeleteEvent
 */
observedArray.splice(0, 1);

// Remove the change observer
changeObserver.cancel();

A short example with an object.

import {ObjectObserverFactory} from 'typescript-object-observer'
type StringDict = {[index : string] : string};

let objectObserver = ObjectObserverFactory.newInstance<StringDict>({}, {
        enableFallback: false
    }),
    observedArray = objectObserver.getObserved();

objectObserver.on('change', data => {
    console.log('ChangeEvent');
});

/*
 * Prints:
 * Object changed
 */
observedArray['foo'] = 'bar';

Contribute

Make sure to run the tests

npm test