ds4/src/module/fonts.ts

type CSSOMString = string;
type FontFaceLoadStatus = "unloaded" | "loading" | "loaded" | "error";
type FontFaceSetStatus = "loading" | "loaded";

interface FontFace {
    family: CSSOMString;
    style: CSSOMString;
    weight: CSSOMString;
    stretch: CSSOMString;
    unicodeRange: CSSOMString;
    variant: CSSOMString;
    featureSettings: CSSOMString;
    variationSettings: CSSOMString;
    display: CSSOMString;
    readonly status: FontFaceLoadStatus;
    readonly loaded: Promise<FontFace>;
    load(): Promise<FontFace>;
}

interface FontFaceSet {
    readonly status: FontFaceSetStatus;
    readonly ready: Promise<FontFaceSet>;
    check(font: string, text?: string): boolean;
    load(font: string, text?: string): Promise<FontFace[]>;
}

declare global {
    interface Document {
        fonts: FontFaceSet;
    }
}

const fonts = ["Lora", "Wood Stamp"];

export async function preloadFonts() {
    return Promise.all(fonts.map((font) => document.fonts.load(`1rem ${font}`)));
}