Ignore Typescript Errors "property does not exist on value of type"

I know the question is already closed but I've found it searching for same TypeScriptException, maybe some one else hit this question searching for this problem.

The problem lays in missing TypeScript typing:

var coordinates = outerElement[0].getBBox();

Throws The property 'getBBox' does not exist on value of type 'HTMLElement'.

The easiest way is to explicitly type variable as `any`

var outerHtmlElement: any = outerElement[0];
var coordinates = outerHtmlElement.getBBox();

Edit, late 2016

Since TypeScript 1.6, the prefered casting operator is as, so those lines can be squashed into:

let coordinates = (outerElement[0] as any).getBBox();

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Other solutions

Of course if you'd like to do it right, which is an overkill sometimes, you can:

1. Create own interface which simply extends HTMLElement
2. Introduce own typing which extends HTMLElement

The quick and dirty solution is to explicitly cast to any

(y as any).x

The "advantage" is that, the cast being explicit, this will compile even with the noImplicitAny flag set.

The proper solution is to update the typings definition file.

Please note that, when you cast a variable to any, you opt out of type checking for that variable.

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Since I am in disclaimer mode, double casting via any combined with a new interface, can be useful in situations where

• you do not want to update a broken typings file
• and/or you are monkey patching

yet, you still want some form of typing.

Say you want to patch the definition of an instance of y of type OrginalDef with a new property x of type number:

const y: OriginalDef = ...

interface DefWithNewProperties extends OriginalDef {
    x: number
}

const patched = y as any as DefWithNewProperties

patched.x = ....   //will compile

You can also use the following trick:

y.x = "some custom property"//gives typescript error

y["x"] = "some custom property"//no errors

Note, that to access x and dont get a typescript error again you need to write it like that y["x"], not y.x. So from this perspective the other options are better.