ionic-framework/core/src/utils/theme.ts

import { CssClassMap, Mode, RouterDirection } from '../interface';

export function hostContext(selector: string, el: HTMLElement): boolean {
  return !!el.closest(selector);
}

/**
 * Create the mode and color classes for the component based on the classes passed in
 */
export function createColorClasses(color: string | undefined): CssClassMap | null {
  return (color) ? {
    'ion-color': true,
    [`ion-color-${color}`]: true
  } : null;
}

export function createThemedClasses(mode: Mode | undefined, name: string): CssClassMap {
  return {
    [name]: true,
    [`${name}-${mode}`]: !!mode
  };
}

export function getClassList(classes: string | string[] | undefined): string[] {
  if (classes) {
    const array = Array.isArray(classes) ? classes : classes.split(' ');
    return array
      .filter(c => c != null)
      .map(c => c.trim())
      .filter(c => c !== '');
  }
  return [];
}

export function getClassMap(classes: string | string[] | undefined): CssClassMap {
  const map: CssClassMap = {};
  getClassList(classes).forEach(c => map[c] = true);
  return map;
}

export async function openURL(win: Window, url: string | undefined, ev: Event, direction?: RouterDirection) {
  if (url && url[0] !== '#' && url.indexOf('://') === -1) {
    const router = win.document.querySelector('ion-router');
    if (router) {
      if (ev) {
        ev.preventDefault();
      }
      await router.componentOnReady();
      return router.push(url, direction);
    }
  }
  return Promise.resolve();
}