Bind function call in object

Question

Goal : Execute function when function -defined in object- is called

Example:

var obj = {
    endUpdate: function(){
       ... (async stuff from library, cannot modify this code)
    }
}

I want to write something like this, to know when endUpdate has been called

obj.on('endUpdate', function(){
    // do stuff here when "endUpdate" in above object is called
})

Answer 1

You can create a subscriber function quite easily like so

var obj = {
   listeners: {
      endUpdate: []
   },
   on: function(name, callbackFn){
      this.listeners[name].push(callbackFn);
   },
   runListeners: function(name) {
      this.listeners[name].forEach((fn) => fn());
   },
   endUpdate: async function(){
       await someStuffFromLib();
       this.runListeners('endUpdate');
   }
}

Otherwise you can enhance the object and chain async functions as long as you maintain the chain all the way through

 var obj = {
   endUpdate: function(){
      const thisIsAPromise = someStuffFromLib();
      return thisIsAPromise;
   }
}

const newObj = {
    endUpdate: (...args) => obj.endUpdate(...args).then(
                (result) => { console.log(result)})
}