DOMStringMap is defined as an empty interface - this makes it awkward to use

[sccolbert]

The DOMStringMap interface is defined as follows:

https://github.com/Microsoft/TypeScript/blob/master/src/lib/dom.generated.d.ts#L10556

interface DOMStringMap {
}
declare var DOMStringMap: {
    prototype: DOMStringMap;
    new(): DOMStringMap;
}

This means it's a compile error to directly access the object properties, but it's also an implicit any error if the --noImplicitAny switch is turned on in the compiler. This makes using a node's dataset somewhat arduous since a cast is required.

I'm not sure if there is some way to declare that an object has arbitrary properties of some given type, but perhaps a minimal working solution would be to give this interface a string indexer:

interface DOMStringMap {
  [key: string]: string;
}

[danquirk]

Seems like there are a few different methods on this type that aren't currently represented in the .d.ts: https://developer.mozilla.org/en-US/docs/Web/API/DOMStringMap. All of them would still be satisfied with that string indexer signature.

[saschanaz]

The methods described in MDN are not implemented in any of three major web browsers including Firefox.

W3C: http://www.w3.org/TR/html5/infrastructure.html#domstringmap

I hope TS allow node.dataset.x way as written in W3C example...