predix-ui/src/utils/mitt.js

px-* web components as React styled components

/* eslint-disable */
export default function mitt(all) {
  all = all || Object.create(null);

  return {
    /**
     * Register an event handler for the given type.
     *
     * @param  {String} type Type of event to listen for, or `"*"` for all events
     * @param  {Function} handler Function to call in response to given event
     * @memberOf mitt
     */
    on(type, handler) {
      (all[type] || (all[type] = [])).push(handler);
    },

    /**
     * Remove an event handler for the given type.
     *
     * @param  {String} type Type of event to unregister `handler` from, or `"*"`
     * @param  {Function} handler Handler function to remove
     * @memberOf mitt
     */
    off(type, handler) {
      if (all[type]) {
        all[type].splice(all[type].indexOf(handler) >>> 0, 1);
      }
    },

    /**
    * Invoke all handlers for the given type.
    * If present, `"*"` handlers are invoked after type-matched handlers.
    *
    * @param {String} type  The event type to invoke
    * @param {Any} [evt]  Any value (object is recommended and powerful), passed to each handler
    * @memberOf mitt
    */
    emit(type, evt) {
      (all[type] || [])
        .slice()
        .map((handler) => {
          handler(evt);
        });
      (all['*'] || [])
        .slice()
        .map((handler) => {
          handler(type, evt);
        });
    }
  };
}