ElementTraversal: missing some nulls

[tkrotoff]

Inside dom.generated.d.ts:

interface ElementTraversal {
    readonly childElementCount: number;
    readonly firstElementChild: Element;
    readonly lastElementChild: Element;
    readonly nextElementSibling: Element;
    readonly previousElementSibling: Element;
}

should be:

interface ElementTraversal {
    readonly childElementCount: number;
    readonly firstElementChild: Element | null;
    readonly lastElementChild: Element | null;
    readonly nextElementSibling: Element | null;
    readonly previousElementSibling: Element | null;
}

Example: https://jsfiddle.net/tkrotoff/khzbrkpg/

(tested with typescript@2.2.0-dev.20161125 lib.dom.d.ts)

[mhegazy]

PRs welcomed. You can find more information about contributing lib.d.ts fixes at https://github.com/Microsoft/TypeScript/blob/master/CONTRIBUTING.md#contributing-libdts-fixes.

[perryjiang]

Hi, I'm new to OSS. If I understand the issue right, this looks like a relatively simple problem? If so, I'd be glad to tackle it.

[mhegazy]

This should be a simple one to change. the change should be done in https://github.com/Microsoft/TSJS-lib-generator, you will need to edit https://github.com/Microsoft/TSJS-lib-generator/blob/master/inputfiles/overridingTypes.json to include the | null.

[perryjiang]

Thanks! PR submitted.