How to get around property does not exist on 'Object'

Question

I'm new to Typescript, and not sure how to word this question.

I need to access two "possible" properties on an object that is passed in the constructor. I know im missing some checks to see if they are defined, but Typescript is throwing me a "Property does not exist on 'Object'" message. The message appears on the selector and template returns.

class View {     public options:Object = {};     constructor(options:Object) {        this.options = options;    }     selector ():string {        return this.options.selector;    }        template ():string {        return this.options.template;    }        render ():void {     }    } 

I'm sure its fairly simple, but Typescript is new to me.

Answer 1

If you don't want to change the type or create an interface, you can also use this syntax to access unknown properties:

selector ():string {     return this.options["selector"]; }     template ():string {     return this.options["template"]; } 

Answer 2

If you use the any type instead of Object, you can access any property without compile errors.

However, I would advise to create an interface that marks the possible properties for that object:

interface Options {   selector?: string   template?: string } 

Since all of the fields use ?:, it means that they might or might not be there. So this works:

function doStuff(o: Options) {   //... }  doStuff({}) // empty object doStuff({ selector: "foo" }) // just one of the possible properties doStuff({ selector: "foo", template: "bar" }) // all props 

If something comes from javascript, you can do something like this:

import isObject from 'lodash/isObject'  const myOptions: Options = isObject(somethingFromJS) // if an object     ? (somethingFromJS as Options) // cast it     : {} // else create an empty object  doStuff(myOptions) // this works now 

Of course this solution only works as expected if you are only unsure about the presence of a property not of it's type.