original_string: public final function once( $eventName, $eventCallback ) {
  
  			if ( !is_string( $eventName ) ) {
  			
  				throw new \browserfs\Exception('Invalid argument $eventName: string expected');
  			
  			} else {
  			
  				if ( !strlen( $eventName ) ) {
  			
  					throw new \browserfs\Exception('Invalid argument $eventName: expected non-empty string');
  			
  				} else {
  			
  					if ( !is_callable( $eventCallback ) ) {
  			
  						throw new \browserfs\Exception('Invalid argument $eventCallback: callable expected' );
  			
  					} else {
  
  						$this->events[ $eventName ] = isset( $this->events[ $eventName ] ) ? $this->events[ $eventName ] : [];
  
  						$this->events[ $eventName ][] = [
  							'once' => true,
  							'callback' => $eventCallback,
  							'fireId' => 0
  						];
  					}
  				}
  			}
  		}
code: public final function once( $eventName, $eventCallback ) {
  
  			if ( !is_string( $eventName ) ) {
  			
  				throw new \browserfs\Exception('Invalid argument $eventName: string expected');
  			
  			} else {
  			
  				if ( !strlen( $eventName ) ) {
  			
  					throw new \browserfs\Exception('Invalid argument $eventName: expected non-empty string');
  			
  				} else {
  			
  					if ( !is_callable( $eventCallback ) ) {
  			
  						throw new \browserfs\Exception('Invalid argument $eventCallback: callable expected' );
  			
  					} else {
  
  						$this->events[ $eventName ] = isset( $this->events[ $eventName ] ) ? $this->events[ $eventName ] : [];
  
  						$this->events[ $eventName ][] = [
  							'once' => true,
  							'callback' => $eventCallback,
  							'fireId' => 0
  						];
  					}
  				}
  			}
  		}
code_tokens: public final function once ( $ eventName , $ eventCallback ) { if ( ! is_string ( $ eventName ) ) { throw new \ browserfs \ Exception ( 'Invalid argument $eventName: string expected' ) ; } else { if ( ! strlen ( $ eventName ) ) { throw new \ browserfs \ Exception ( 'Invalid argument $eventName: expected non-empty string' ) ; } else { if ( ! is_callable ( $ eventCallback ) ) { throw new \ browserfs \ Exception ( 'Invalid argument $eventCallback: callable expected' ) ; } else { $ this -> events [ $ eventName ] = isset ( $ this -> events [ $ eventName ] ) ? $ this -> events [ $ eventName ] : [ ] ; $ this -> events [ $ eventName ] [ ] = [ 'once' => true , 'callback' => $ eventCallback , 'fireId' => 0 ] ; } } } }
docstring: Adds a event listener that will be fired only once.
  @param eventName: string
  @param eventCallback: callable( $e: \browserfs\Event ) => void
  @throws \browserfs\Exception
docstring_tokens: Adds a event listener that will be fired only once .