Question

How do I create a new object in javascript based on a variable type-string (containing the name of the object)?

Now I have: (with more tools coming the list will get longer…)

function getTool(name){
  switch(name){
    case "SelectTool":
      return new SelectTool();
      break;
    case "LineTool":
      return new LineTool();
      break;
    case "BlurTool":
      return new BlurTool();
      break;
    case "PointerTool":
    default:
      return new PointerTool();
      break;
  }
}

And defined my tools like:

PointerTool.prototype = new Tool;
PointerTool.prototype.constructor = PointerTool;
function PointerTool(){
  this.name = "PointerTool";
}
PointerTool.prototype.click = function(x, y){
  info("You clicked at: "+x+", "+y);
}

I would like to get ride of the (growing) switch statement, it seems ‘wrong’.

Answer 1

function getTool(name){
  return ( typeof window[name] === 'function' ) ? 
                                    new window[name]() : {/*some default*/};
}

Assumes PointerTool constructor is defined in the global window namespace. Replace that with whatever namespace you’re using.