The simple calculator

calculator 1.0.0

'use strict';

var Calculator = function() {
	var obj = this, a, b, c;

	var allValue = {
  	'+': function() {
    	return a + b;
    },
    '-': function() {
    	return a - b;
    },
    '/': function() {
    	return a / b;
    },
    '*': function() {
    	return a * b;
    }
  }; 
	
  this.getReady = function() {
  
   	a = +prompt('First number', '');
  	b = +prompt('Last number', '');
		c =  prompt('Your action', ''); 
    checkOut();
  }
  
  this.getAnswer = function() {
  	alert(allValue[c]());
  };
  
	function check() {
  	if(isNaN(a) || isNaN(b) || !allValue[c]) {
    	alert('Sorry, but your entry is uncorrect')
    } else {
    	return obj.getAnswer();
    }
  }
  
};

var calc = new Calculator();

calc.getReady();