const toString = Object . prototype . toString ; export function isString ( o ) { return typeof o === 'string' || o instanceof String ; } export function isBool ( o ) { return o === true || o === false || ( toString . call ( o ) === '[object Boolean]' ) ; } export function isFunction ( o ) { return typeof o === 'function' ; } export function isNumber ( o ) { return typeof o === 'number' || ( toString . call ( o ) === '[object Number]' ) ; }