export class RandomUtil { private static _keys = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=" ; static randomString ( length ) { let str = "" ; for ( let i = 0 ; i < length ; i ++ ) { str += this . _keys [ Math . floor ( ( this . _keys . length - 1 ) * Math . random ( ) ) ] ; } return str ; } }