export function isString ( o ) { return typeof o === 'string' ; } export function isUndefined ( o ) { return typeof o === 'undefined' ; } export function isNull ( o ) { return o === null ; } export function isObject < T > ( o ) { return o !== null && typeof o === 'object' ; } export function isBoolean ( o ) { return o === true || o === false ; } export function isFunction ( o ) { return typeof o === 'function' ; } export function isNumber ( o ) { return typeof o === 'number' ; } export function isBooleanStringLiteral ( o ) { return o === 'true' || o === 'false' ; } export const isArray = Array . isArray ;