documentcloud/underscore — pull request #1013 by vasa-c (2013-03-13 09:17:25+00:00)
Title: Fix _.isFunction (IE < 9 and host-functions)

In Internet Explorer (< version 9) host-functions is always "object":

typeof alert === "object"

Object.prototype.toString.call(document.getElementById) === "[object Object]".

_.isFunction(alert); // false in IE7,8
_.isFunction(document.getElementById); // false in IE7,8