export function isString ( value ) { return typeof value === 'string' ; } export function isNumber ( value ) { return typeof value === 'number' && parseInt ( `${ value }` , 10 ) === value ; } export function isFunction ( value ) { return typeof value === 'function' ; } export function isObject ( value ) { return Object . prototype . toString . call ( value ) === '[object Object]' ; } export function isPromise ( value ) { return value instanceof Promise ; }