NativeScript/nativescript-core/css/system-classes.ts

const MODAL = "modal";
const ROOT = "root";
const cssClasses = [];

export const CLASS_PREFIX = "ns-";
export const MODAL_ROOT_VIEW_CSS_CLASS = `${CLASS_PREFIX}${MODAL}`;
export const ROOT_VIEW_CSS_CLASS = `${CLASS_PREFIX}${ROOT}`;

export function getSystemCssClasses(): string[] {
    return cssClasses;
}

export function pushToSystemCssClasses(value: string): number {
    cssClasses.push(value);

    return cssClasses.length;
}

export function removeSystemCssClass(value: string): string {
    const index = cssClasses.indexOf(value);
    let removedElement;

    if (index > -1) {
        removedElement = cssClasses.splice(index, 1);
    }

    return removedElement;
}

export function getModalRootViewCssClass(): string {
    return MODAL_ROOT_VIEW_CSS_CLASS;
}

export function getRootViewCssClasses(): string[] {
    return [ROOT_VIEW_CSS_CLASS, ...cssClasses];
}

export function pushToRootViewCssClasses(value: string): number {
    return pushToSystemCssClasses(value) + 1; // because of ROOT_VIEW_CSS_CLASS
}

export function removeFromRootViewCssClasses(value: string): string {
    return removeSystemCssClass(value);
}