in scripts/build.js [542:557]
function parse(what, how) {
if (!how || typeof how === 'function') {
how = {callback: how};
}
// if first argument is string, inject html <img> tags
// otherwise use the DOM tree and parse text nodes only
return (typeof what === 'string' ? parseString : parseNode)(what, {
callback: how.callback || defaultImageSrcGenerator,
attributes: typeof how.attributes === 'function' ? how.attributes : returnNull,
base: typeof how.base === 'string' ? how.base : twemoji.base,
ext: how.ext || twemoji.ext,
size: how.folder || toSizeSquaredAsset(how.size || twemoji.size),
className: how.className || twemoji.className,
onerror: how.onerror || twemoji.onerror
});
}