Asynchronous constructor

Question

How can I best handle a situation like the following?

I have a constructor that takes a while to complete.

var Element = function Element(name){
            


        

Answer 1

One thing you could do is preload all the nuclei (maybe inefficient; I don't know how much data it is). The other, which I would recommend if preloading is not an option, would involve a callback with a cache to save loaded nuclei. Here is that approach:

Element.nuclei = {};

Element.prototype.load_nucleus = function(name, fn){
   if ( name in Element.nuclei ) {
       this.nucleus = Element.nuclei[name];
       return fn();
   }
   fs.readFile(name+'.json', function(err, data) {
      this.nucleus = Element.nuclei[name] = JSON.parse(data); 
      fn();
   });
}