Evented#removeListener
As a conscious TODO: need to properly handle attaching the same event listener multiple times (define its behavior), and maybe even provide an API to configure that behavior in some way.events
Mike Gerwitz
parent
7baff379ce
commit
981d8b923a
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@ -20,7 +20,10 @@
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*/
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var Trait = require( 'easejs' ).Trait,
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isArray = require( '../std/Array' ).isArray;
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isArray = require( '../std/Array' ).isArray,
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// used for hiding cached event indexes
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_evid = Symbol();
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/**
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@ -42,6 +45,12 @@ module.exports = Trait( 'Evented',
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*/
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_events: {},
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/**
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* List of gaps in event callback lists
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* @type {Object}
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*/
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_gaps: {},
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/**
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* Defines a list of events by unique identifier
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@ -89,7 +98,8 @@ module.exports = Trait( 'Evented',
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}
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// will contain each callback associated with this event
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this._events[ ids[ i ] ] = [];
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this._events[ id ] = [];
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this._gaps[ id ] = [];
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}
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},
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@ -131,7 +141,7 @@ module.exports = Trait( 'Evented',
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* provides different guarantees.
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*
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* @param {string} ev defined event id
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* @param {Array.<Function>} evc event callbacks (hooks)
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* @param {Array.<Function>} evc event callbacks (listeners)
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* @param {Array} args argument list to apply to callbacks
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*
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* @return {Evented} self
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@ -140,8 +150,9 @@ module.exports = Trait( 'Evented',
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{
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var i = evc.length;
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// note that there may be gaps (see _gaps)
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while ( i-- ) {
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evc[ i ].apply( null, args );
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evc[ i ] && evc[ i ].apply( null, args );
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}
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return this;
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@ -149,28 +160,104 @@ module.exports = Trait( 'Evented',
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/**
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* Invoke callback when an event is emitted
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* Invoke listener when an event is emitted
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*
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* The event EV must be defined and CALLBACK must be a function. The
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* The event EV must be defined and LISTENER must be a function. The
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* context in which the callback is invoked (the value of `this') is
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* undefined.
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*
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* @O {#hookEvent} depends on hooking algorithm
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*
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* @param {string} ev defined event id
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* @param {Function} callback function to invoke when event is emitted
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* @param {Function} listener function to invoke when event is emitted
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*
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* @return {Evented} self
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*/
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on( ev, callback )
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on( ev, listener )
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{
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if ( !( this._events[ ev ] ) ) {
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throw Error( "Cannot hook undefined event `" + ev + "'" );
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throw Error( `Cannot hook undefined event \`${ev}'` );
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}
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else if ( typeof callback !== 'function' ) {
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throw TypeError( "Event callback must be a function" );
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else if ( typeof listener !== 'function' ) {
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throw TypeError( "Event listener must be a function" );
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}
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this._events[ ev ].push( callback );
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this.hookEvent( ev, listener );
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return this;
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}
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},
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/**
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* Adds event listener, ensuring that gaps created by removing listeners
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* are filled if available
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*
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* Listeners are added in constant time. A field is set on LISTENER to
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* cache the index, allowing for removing listeners in constant time.
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*
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* Subtypes may use this to alter hook behavior by preventing the hook
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* (by not forwarding the listener to __supet) and instead invoke
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* __super with a new listener, possibly wrapping the original.
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*
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* @param {string} ev defined event id
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* @param {Function} listener function to invoke when event is emitted
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*
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* @return {Evented} self
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*/
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'virtual protected hookEvent'( ev, listener )
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{
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let evls = this._events[ ev ],
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avail = this._gaps[ ev ].pop();
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if ( avail === undefined ) {
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listener[ _evid ] = evls.length;
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evls.push( listener );
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}
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else {
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listener[ _evid ] = avail;
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evls[ avail ] = listener;
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}
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return this;
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},
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/**
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* Removes a previously hooked listener in constant time, preventing it
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* from being invoked on future emits of event EV
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*
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* EV must be a valid event identifier. If LISTENER is not registered
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* for event id EV, no error will occur (since it fulfills the criteria
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* that it will not be subsequently invoked by event EV).
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*
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* Listeners are compared by reference---the exact listener that was
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* registered with EV must be passed for removal.
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*
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* @param {string} ev defined event id
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* @param {Function} listener listener to remove
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*
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* @return {Evented} self
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*
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* @throws {Error} when EV is not a defined event identifier
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*/
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removeListener( ev, listener )
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{
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if ( !( this._events[ ev ] ) ) {
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throw Error( `Cannot unhook undefined event \`${ev}'` );
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}
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let evls = this._events[ ev ],
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index = listener[ _evid ];
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// this is important, since we (a) cannot necessarily trust that the
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// cached index hasn't been forged and (b) if a listener is removed
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// multiple times, the index may contain a different listener
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if ( evls[ index ] === listener )
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{
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evls[ index ] = undefined;
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this._gaps[ ev ].push( index );
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}
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return this;
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},
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} );
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@ -353,5 +353,218 @@ describe( 'event.Evented', () =>
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.evEmit( ev );
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} );
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} );
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/**
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* Permits additional actions on hook and overriding event hooking
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* storage behavior
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*/
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describe( '#hookEvent', function()
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{
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var ev = 'foo',
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f = ()=>{};
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it( 'can be overridden by subtypes', ( done ) =>
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{
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common.checkOverride( EvStub, 'hookEvent',
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( given_ev, given_callback ) =>
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{
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expect( given_ev ).to.equal( ev );
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expect( given_callback ).to.equal( f );
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done();
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}
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)().evDefineEvents( [ ev ] ).on( ev, f );
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} );
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/**
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* Should provide full control over how the listeners are handled.
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*/
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it( 'can prevent listeners from being added', () =>
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{
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var ev = 'foo';
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// override does nothing
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expect( () =>
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{
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EvStub.extend(
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{
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'override hookEvent': ( _, __ ) => {}
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} )()
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.evDefineEvents( [ ev ] )
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.on( ev, () =>
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{
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throw Error( "Event called!" );
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} ).evEmit( ev );
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} ).to.not.throw( Error );
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} );
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} );
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describe( '#removeListener', () =>
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{
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it( 'rejects unknown event ids', () =>
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{
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var ev = 'foo';
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expect( () => stub.removeListener( ev , ()=>{} ) )
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.to.throw( Error, ev );
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} );
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/**
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* The purpose of removing a listener is to prevent it from being
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* called when an event is emitted. We don't really care how this is
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* done; just don't call it.
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*/
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it( 'prevents removed listener from being called', () =>
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{
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var ev = 'foo',
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called = false,
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listener = ( () => called = true );
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stub.evDefineEvents( [ ev ] );
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// we have already proved that adding a listener works;
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// immediately remove it and ensure that it's not called
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stub.on( ev, listener )
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.removeListener( ev, listener );
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stub.evEmit( ev );
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expect( called ).to.equal( false );
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} );
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/**
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* If the given listener to remove was never registered (or no
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* longer is), then we will shall act as though it was successfully
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* removed (since, according to our initial requirement, we
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* succeeded in ensuring that the listener will not be called on
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* subsequent emits).
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*/
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it( 'does not fail and returns self on missing listener', () =>
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{
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let ev = 'foo';
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expect(
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stub.evDefineEvents( [ ev ] )
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.removeListener( ev, () => {} )
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).to.equal( stub );
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} );
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it( 'returns self on success', () =>
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{
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let ev = 'foo',
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f = () => {};
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expect(
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stub.evDefineEvents( [ ev ] )
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.on( ev, f )
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.removeListener( ev, f )
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).to.equal( stub );
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} );
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/**
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* These are tests that are not design per se, but are intended to
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* comprehensively guard against future design changes, likely or
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* not.
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*/
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describe( 'sanity check', () =>
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{
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/**
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* Removing a single listener for an event should not touch
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* others for that same event
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*/
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it( 'does not remove all listeners for event', () =>
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{
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var ev = 'foo',
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f1c = false,
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f2c = false,
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f1 = () => f1c = true,
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f2 = () => f2c = true;
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stub.evDefineEvents( [ ev ] )
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.on( ev, f1 )
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.on( ev, f2 )
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.removeListener( ev, f1 )
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.evEmit( ev );
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expect( f1c ).to.be.false;
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expect( f2c ).to.be.true;
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} );
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/**
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* The same listener may be added to multiple events---we should
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* only ever remove it from the one that was requested. We have
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* already proven in previous tests that event listeners are
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* actually removed as expected, so we need only ensure that it
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* is *not* removed from another event that it is attached to.
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*/
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it( 'does not remove same listener on other events', () =>
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{
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var evs = [ 'foo', 'bar' ],
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called = false,
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f = () => called = true;
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stub.evDefineEvents( evs )
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.on( evs[ 0 ], f )
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.on( evs[ 1 ], f )
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.removeListener( evs[ 0 ], f )
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.evEmit( evs[ 1 ] );
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expect( called ).to.be.true;
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} );
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/**
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* Removing a listener may introduce, depending on
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* implementation details that we do not care about here, gaps
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* in the data structure holding the listeners. The idea here is
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* to ensure that this gap, if immediately filled, will not
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* cause problems.
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*/
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it( 'can add listener after removal', () =>
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{
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var ev = 'foo',
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called = 0,
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frm = () => {},
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fok = () => called++,
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fok2 = () => called += 2;
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stub.evDefineEvents( [ ev ] )
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.on( ev, frm )
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.removeListener( ev, frm )
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.on( ev, fok )
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.on( ev, fok2 )
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.evEmit( ev );
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expect( called ).to.equal( 3 );
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} );
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/**
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* Similar to the above test, but ensures that the system is not
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* marking a listener for deletion in such a way that it won't
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* be recognized later. This would be an odd implementation, but
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* people do odd things sometimes.
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*/
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it( 'can re-add removed listener', () =>
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{
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var ev = 'foo',
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called = false,
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f = () => called = true;
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stub.evDefineEvents( [ ev ] )
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.on( ev, f )
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.removeListener( ev, f )
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.on( ev, f )
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.evEmit( ev );
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expect( called ).to.be.true;
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} );
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} );
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} );
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} );
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