node.js如何向字符串添加onchange事件

Question

Is it possible to add an onchange event to a string ?

I want something like this:

var myString = '';
var doSomething = function(){
   console.log('string changed');
};

myString.on('change',doSomething);
myString = 'new'; //at this point the on('change') event should be run

Answer 1

No, this is not possible as strings are immutable in JavaScript.

Any string operation that appears as though it's changing a string is actually creating a new string.

So, even if you were to somehow attach events to String.prototype , there's no way to detect a change since a string can never change

Answer 2

Because of the answer of "macek" (thanks by the way) this is not a right answer, but a "workaround" thats works good for me. Maybe someone else helps this too.

var events = require('events');

var myString = function(val){
   this.myVal = val;

   this.change = function(newVal)
   {
       if(newVal !== this.myVal){
           this.myVal = newVal;
           this.emit('changed');
       }
   }
   this.val = function(){
      return this.myVal;
   }

};

myString.prototype.__proto__ = events.EventEmitter.prototype;

var doSomething = function(){
    console.log('string changed');
};

var somestring = new myString('');

console.log(somestring.val()); // output ''
somestring.on('changed',doSomething);
somestring.change('new'); //output doSomething() -> 'string changed'
console.log(somestring.val()); //output 'new'