Underscore object functions

// keeps key/value associations
_.mixin({
    // similar to _.map
    objMap: function( input, mapper, context ) {
        return _.reduce( input, function (obj, v, k) {
            obj[k] = mapper.call( context, v, k, input );
            return obj;
        }, {}, context);
    },
    // similar to _.filter
    objFilter: function( input, test, context ) {
        return _.reduce( input, function (obj, v, k) {
            if( test.call( context, v, k, input )) {
                obj[k] = v;
            }
            return obj;
        }, {}, context);
    },
    // similar to _.reject
    objReject: function( input, test, context ) {
        return _.reduce( input, function (obj, v, k) {
            if( !test.call( context, v, k, input )) {
                obj[k] = v;
            }
            return obj;
        }, {}, context);
    }
});