通过 Object.prototype.toString.call() 进行类型判断

type.coffee

# http://zhang.zipeng.info/library/coffeescript/07_the_bad_parts.html
# 使用typeof
# 这里是jQuery的$.type的实现的例子

type = do ->
	classToType = {}
	for name in "Boolean Number String Function Array Date RegExp Undefined Null".split(" ")
		classToType["[object " + name + "]"] = name.toLowerCase()

	(obj) ->
		strType = Object::toString.call(obj)
		classToType[strType] or "object"

# Returns the sort of types we'd expect:
# type("")         # "string"
# type(new String) # "string"
# type([])         # "array"
# type(/\d/)       # "regexp"
# type(new Date)   # "date"
# type(true)       # "boolean"
# type(null)       # "null"
# type({})         # "object"

typeof.js

// http://my.oschina.net/sfm/blog/33197
var oP = Object.prototype,
toString = oP.toString;

function typeOf(value) {
    if (null === value) {
        return 'null';
    }

    var type = typeof value;
    if ('undefined' === type || 'string' === type) {
        return type;
    }

    var typeString = toString.call(value);
    switch (typeString) {
        case '[object Array]':
            return 'array';
        case '[object Date]':
            return 'date';
        case '[object Boolean]':
            return 'boolean';
        case '[object Number]':
            return 'number';
        case '[object Function]':
            return 'function';
        case '[object RegExp]':
            return 'regexp';
        case '[object Object]':
            if (undefined !== value.nodeType) {
                if (3 == value.nodeType) {
                    return (/\S/).test(value.nodeValue) ? 'textnode': 'whitespace';
                } else {
                    return 'element';
                }
            } else {
                return 'object';
            }
        default:
            return 'unknow';
    }
}