gistfile1.txt

function make_adder( left_operand ) { 
	return function ( right_operand ) { 
		return left_operand + right_operand; 
	}; 
}

so, you can say:
var plus_two = make_adder(2);
var plus_three = make_adder(3);
alert(plus_two(5));
alert(plus_three(5));