Take action upon being added to a collection or being observed

Consider the following scenario: I have an array called "x" and an Observable created from this array (arrObs). There is a button on the page, and when a user clicks on it, a random number is added to the array. The goal is to display the newly added value from the array whenever a new value is pushed into it.

http://jsbin.com/sovuyipuju/edit?js,console,output

var x = [1,2,3,4];
var clicks = Rx.Observable.fromEvent(document.querySelector('#button1'),'click');
clicks
  .map(function(y){return Math.floor(Math.random()*50)})
  .subscribe(function(z){  x.push(z);});

arrObs = Rx.Observable.from(x);
arrObs
  .map(function(x){  return x*2;})
  .subscribe(function(value){console.log(value);
});

Answer №1

Employing only vanilla JavaScript:

var array=[];
array.customPush=array.push.bind(array);
array.push=function(...args){
  args.forEach(item => console.log(item));
  this.customPush(...args);
};

(I believe using a framework is unnecessary in this case...)

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