function isNumber(obj) { return obj === +obj } function isString(obj) { return obj === obj+'' } function isBoolean(obj) { return obj === !!obj } function isPlainObject(obj) { return Object.keys(obj).length == 0 }
function isNumber(obj) { return obj === +obj } function isString(obj) { return obj === obj+'' } function isBoolean(obj) { return obj === !!obj } function isPlainObject(obj) { return Object.keys(obj).length == 0 }