object.js

var object = {
	extend: function (obj) {
		var i = 1, key, len = arguments.length;
		for (; i < len; i += 1) {
			for (key in arguments[i]) {
				// make sure we do not override built-in methods but toString and valueOf
				if (arguments[i].hasOwnProperty(key) && 
					(!obj[key] || obj.propertyIsEnumerable(key) || key === 'toString' || key === 'valueOf')) {
					obj[key] = arguments[i][key];
				}
			}
		}
		return obj;
	},
    
    filter: function (obj, fun, thisObj) {
        var key, r = {}, val;
        thisObj = thisObj || obj;
        for (key in obj) {
            if (obj.hasOwnProperty(key)) {
                val = obj[key];
                if (fun.call(thisObj, val, key, obj)) {
                    r[key] = val;
                }
            }
        }
        return r;
    },

    map: function (obj, fun, thisObj) {
        var key, r = {};
        thisObj = thisObj || obj;
        for (key in obj) {
            if (obj.hasOwnProperty(key)) {
                r[key] = fun.call(thisObj, obj[key], key, obj);
            }
        }
        return r;
    },

    forEach: function (obj, fun, thisObj) {
        var key;
        thisObj = thisObj || obj;
        for (key in obj) {
            if (obj.hasOwnProperty(key)) {
                fun.call(thisObj, obj[key], key, obj);			
            }
        }
    },

    every: function (obj, fun, thisObj) {
        var key;
        thisObj = thisObj || obj;
        for (key in obj) {
            if (obj.hasOwnProperty(key) && !fun.call(thisObj, obj[key], key, obj)) {
                return false;
            }
        }
        return true;
    },

    some: function (obj, fun, thisObj) {
        var key;
        thisObj = thisObj || obj;
        for (key in obj) {
            if (obj.hasOwnProperty(key) && fun.call(thisObj, obj[key], key, obj)) {
                return true;
            }
        }
        return false;
    },

    isEmpty: function (obj) {
        return object.every(obj, function (value, key) { 
            return !obj.hasOwnProperty(key); 
        });
    },

    values: function (obj) {
        var r = [];
        object.forEach(obj, function (value) {
            r.push(value);
        });
        return r;
    },

    keys: function (obj) {
        var r = [];
        object.forEach(obj, function (value, key) {
            r.push(key);
        });
        return r;
    },

    reduce: function (obj, fun, initial) {
        var key, initialKey;

        if (object.isEmpty(obj) && initial === undefined) {
            throw new TypeError();
        }
        if (initial === undefined) {
            for (key in obj) {
                if (obj.hasOwnProperty(key)) {
                    initial = obj[key];
                    initialKey = key;
                    break;
                }
            }
        }
        for (key in obj) {
            if (obj.hasOwnProperty(key) && key !== initialKey) {
                initial = fun.call(null, initial, obj[key], key, obj);
            }
        }
        return initial;
    }
};

module.exports = object;