A script that creates functions for operators and operands, which can be used to perform basic math operations.

closureMath.js

/*
 * Creates functions for the numbers 0-9, and also functions for +, -, *, and /.
 * Here is a list of the available functions:
 * Operands: zero(), one(), two(), three(), four(), five(), six(), seven(), eight(), nine();
 * Operators: plus(), minus(), times(), divide();
 *
 * Usage:
 * The Operands ('zero' through 'nine') can be called with or without an operator as an argument.
 * 
 * The Operators ('plus', 'minus', etc..) require that a number be passed as a param, and must be executed within an Operand.
 *
 * Examples:
 *             (0) => zero(); // 0
 *             (9) => nine(); // 9
 *    (3 + 7 = 10) => three(plus(seven())); // 10
 *    (1 - 6 = -5) => one(minus(six())); // -5
 *    (4 * 4 = 16) => four(times(four())); // 16
 *     (8 / 2 = 4) => eight(divide(two())); // 4
 *
 *  plus(); //INVALID (missing operand)
 *  one(two()); // INVALID (no operator)
*/

// Operand Class:
var Operand = function(value){
    return function(operator){
        if(operator instanceof Function){
            return operator(value);
        }else{
            return value;
        }
    };
};

// Operator Class:
var Operator = function(symbol){
    return function(rightOperand){
            return function(leftOperand){
                if(!isNaN(leftOperand) && !isNaN(rightOperand)){
                    switch(symbol){
                        case '+':
                            return leftOperand + rightOperand;
                        case '-':
                            return leftOperand - rightOperand;
                        case '*':
                            return leftOperand * rightOperand;
                        case '/':
                            return leftOperand / rightOperand;
                        default:
                            break;
                    }
                }else{
                    return null;
                }
            };
    };
};

// Function to convert int to english...
var getNumberName = function(num){
    switch(num){
        case 0:
            return 'zero';
        case 1:
            return 'one';
        case 2:
            return 'two';
        case 3:
            return 'three';
        case 4:
            return 'four';
        case 5:
            return 'five';
        case 6:
            return 'six';
        case 7:
            return 'seven';
        case 8:
            return 'eight';
        case 9:
            return 'nine';
        case 10:
            return 'ten';
        default:
            break;
    }
};

// Function to define the methods on the window object...
var defineMathFunctions = function(){
    // Define the operators: (+, -, *, /);
    window['plus'] = new Operator('+');
    window['minus'] = new Operator('-');
    window['times'] = new Operator('*');
    window['divide'] = new Operator('/');
    // Define the operands: (0 - 9);
    for(var i=0; i<10; i++){
        window[getNumberName(i)] = new Operand(i);
    }
};

// Go ahead and define those functions!
defineMathFunctions();

// Some tests to make sure it works as advertised...
var tests = [
    function(){
        var expected1 = 2;
        var result1 = one(plus(one()));
        console.log('1+1=2 : ', result1 === expected1);
        
        var expected2 = 8;
        var result2 = four(plus(four()));
        console.log('4+4=8 : ', result2 === expected2);
    },
    function(){
        var expected1 = 27;
        var result1 = three(times(nine()));
        console.log('3*9=27 : ', result1 === expected1);
        
        var expected2 = 0;
        var result2 = seven(times(zero()));
        console.log('7*0=0 : ', result2 === expected2);
    },
    function(){
        var expected1 = 7;
        var result1 = nine(minus(two()));
        console.log('9-2=7 : ', result1 === expected1);
        
        var expected2 = -7;
        var result2 = one(minus(eight()));
        console.log('1-8=(-7) : ', result2 === expected2);
    },
    function(){
        var expected1 = 4;
        var result1 = eight(divide(two()));
        console.log('8/2=4 : ', result1 === expected1);
        
        var expected2 = 1.2;
        var result2 = six(divide(five()));
        console.log('6/5=1.2 : ', result2 === expected2);
    }
];
tests.forEach(function(test){
    test();
});