isString_.isString(object) Returns true if object is a String. _.isString("moe"); => true

isRegExp_.isRegExp(object) Returns true if object is a RegExp. _.isRegExp(/moe/); => true

isObject_.isObject(value) Returns true if value is an Object. Note that JavaScript arrays and functions are objects, while (normal) strings and numbers are not. _.isObject({}); => true _.isObject(1); => false

isNumber_.isNumber(object) Returns true if object is a Number (including NaN). _.isNumber(8.4 * 5); => true

isNull_.isNull(object) Returns true if the value of object is null. _.isNull(null); => true _.isNull(undefined); => false

isNaN_.isNaN(object) Returns true if object is NaN. Note: this is not the same as the native isNaN function, which will also return true for many other not-number values, such as undefined. _.isNaN(NaN); => true isNaN(undefined); => true _.isNaN(undefined); => false

isMatch_.isMatch(object, properties) Tells you if the keys and values in properties are contained in object. var stooge = {name: 'moe', age: 32}; _.isMatch(stooge, {age: 32}); => true

isFunction_.isFunction(object) Returns true if object is a Function. _.isFunction(alert); => true

isFinite_.isFinite(object) Returns true if object is a finite Number. _.isFinite(-101); => true _.isFinite(-Infinity); => false

isError_.isError(object) Returns true if object inherits from an Error. try { throw new TypeError("Example"); } catch (o_O) { _.isError(o_O); } => true