/**
 * Returns true when `url` resolves to an http(s) URL.
 *
 * Relative URLs are resolved against `base` (the document base URI in a
 * browser), so `/docs` passes while `javascript:`, `data:` and `mailto:` fail.
 * The URL parser lowercases the scheme, trims leading and trailing whitespace
 * and strips embedded tab/newline characters, so `JAVASCRIPT:`, ` javascript:`
 * and `java\tscript:` variants are rejected too.
 */
export declare const isHttpUrl: (url: string, base?: string | undefined) => boolean;
/**
 * Opens `url` in a new tab.
 *
 * `noopener` stops the new page from reaching back into this one through
 * `window.opener` (reverse tabnabbing). Browsers apply it implicitly for
 * `<a target="_blank">` but not for `window.open`. Non-http(s) URLs are
 * refused with a warning, since a `javascript:` URL would otherwise run in
 * this document's origin.
 */
export declare const openInNewTab: (url: string) => void;