export const urlB64ToUint8Array = ( base64String ) : ArrayBuffer => { const padding = "=" . repeat ( ( 4 - ( base64String . length % 4 ) ) % 4 ) ; const base64 = ( base64String + padding ) . replace ( /\-/g , "+" ) . replace ( /_/g , "/" ) ; const rawData = atob ( base64 ) ; const outputArray = new Uint8Array ( rawData . length ) ; for ( let i = 0 ; i < rawData . length ; ++ i ) { outputArray [ i ] = rawData . charCodeAt ( i ) ; } return outputArray ; } ;