Best way to solve typescript error - property does not exist on type

Question

I have several different situations where I am trying to define a self made property on an array or object in typescript but commonly get the error:

"Property x does not exist on type Object (or type Array)"

For example I am using typescript in Angular and have a defined scope based on the Angular type definition file:

scope:ng.IScope

But then when I try to create a new property on scope by doing:

scope.anotherProperty = "string";

I get the error mentioned above. I know I can solve it by doing one of the following:

scope["anotherProperty"] = "string";

OR

(<any>scope).anotherProperty = "string;

Another example is when I have something like this within my d3 graph:

function panZoomNode (node:any) {
            for (var i = 0; i < renderedNodes.length; i++) {
                if (node.id === renderedNodes[i].id) {

                    }
                }
        }

Ideally, I would like to change that (node:any) parameter to something like:

(node:Object)

But when I do that, I get an error saying "property id does not exist on type Object". I know I can correct it with the solutions I mentioned above but that seems kind of sloppy to me. Is there a better way or best typescript way of getting those to run correctly for both arrays and objects?

Thanks

Answer 1

You can add the extra property to the ng.IScope interface by adding the following to your code:

interface ng.IScope {
    anotherProperty?:string;
}

This would allow you to call

scope.anotherProperty = "string";

Without seeing the rest of your code and knowing what node actually represents I can only say that to make the compiler happy you need to just include the members you refer to in your TS code. If you were doing it properly then create a class that contains all members. If it derives from an existing class or implements an existing interface then you should inherit from those in your class definition.

Edit: If you haven't already, you should look in the DefinitelyTyped GitHub repo for the D3 definitions. Assuming node is a D3 type, you can use that to solve your problem and avoid writing your own class.