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

isEmpty_.isEmpty(object) Returns true if an enumerable object contains no values (no enumerable own-properties). For strings and array-like objects _.isEmpty checks if the length property is 0. _.isEmpty([1, 2, 3]); => false _.isEmpty({}); => true

isEqual_.isEqual(object, other) Performs an optimized deep comparison between the two objects, to determine if they should be considered equal. var stooge = {name: 'moe', luckyNumbers: [13, 27, 34]}; var clone = {name: 'moe', luckyNumbers: [13, 27, 34]}; stooge == clone; => false _.isEqual(stooge, clone); => true

isElement_.isElement(object) Returns true if object is a DOM element. _.isElement(jQuery('body')[0]); => true

isDate_.isDate(object) Returns true if object is a Date. _.isDate(new Date()); => true

isBoolean_.isBoolean(object) Returns true if object is either true or false. _.isBoolean(null); => false

isArguments_.isArguments(object) Returns true if object is an Arguments object. (function(){ return _.isArguments(arguments); })(1, 2, 3); => true _.isArguments([1,2,3]); => false

invoke_.invoke(list, methodName, *arguments) Calls the method named by methodName on each value in the list. Any extra arguments passed to invoke will be forwarded on to the method invocation. _.invoke([[5, 1, 7], [3, 2, 1]], 'sort'); => [[1, 5, 7], [1, 2, 3]]

intersection_.intersection(*arrays) Computes the list of values that are the intersection of all the arrays. Each value in the result is present in each of the arrays. _.intersection([1, 2, 3], [101, 2, 1, 10], [2, 1]); => [1, 2]

invert_.invert(object) Returns a copy of the object where the keys have become the values and the values the keys. For this to work, all of your object's values should be unique and string serializable. _.invert({Moe: "Moses", Larry: "Louis", Curly: "Jerome"}); => {Moses: "Moe", Louis: "Larry", Jerome: "Curly"};