How to dynamically exclude the object from the chaininig in JavaScript?

Question

I've got the object structure, where utils and utils.not takes the same prototype (with exist method). I simplified it for make it more clear:

var negative = true;
if(negative){
  //when negative===true, I want to run exist() through not object
  tests.utils.not.exist();
} else {
  tests.utils.exist();
}

Is there any other way to exclude not from the chain instead of using IF? If I wanted to change not object into another, eg positive, I could do this simply like that:

tests.utils[negative ? 'not':'positive'].exist();

But how can I dynamically exclude not object from the chain? My IF syntax works fine, but I just wonder if there is another (more elegant) way in JS.

Answer 1

You can use Proxies to set default behaviour and then call them the way you want take a look at the example

var handler = {
  get: function(target, name) {
    return target.hasOwnProperty(name) ? target[name] : target["default"];
  }
};

var p = new Proxy({
	default : {
		exists : function(){
			return 1;
		}
	},
	not : {
		exists : function(){
			return 2;
		}
	}       
}, handler);

let negative = false;

let x = p[negative === true ? "not" : "default"];
console.log(x.exists());

Take a look at MDN docs