code: function toEmitter( selection, target ){
      
      // Apply the entire Emitter API
      if( selection === API ){
          asEmitter.call( target );
      
      // Apply only the selected API methods
      } else {
          let index, key, mapping, names, value;
          
          if( typeof selection === 'string' ){
              names = selection.split( ' ' );
              mapping = API;
          } else {
              names = Object.keys( selection );
              mapping = selection;
          }
          
          index = names.length;
          
          while( index-- ){
              key = names[ index ];
              value = mapping[ key ];
              
              target[ key ] = typeof value === 'function' ?
                  value :
                  API[ value ];
          }
      }
  }
docs: Applies a `selection` of the Emitter.js API to the `target`.
  @function Emitter~toEmitter
  @param {APIReference} [selection] A selection of the Emitter.js API.
  @param {external:Object} target The object on which the API will be applied.