function valid_percent(){
	var reg = /^100$|^\d{0,2}(\.\d{1,2})?$/;
	var value = document.getElementById("interest_rate").value;
	if(reg.test(value) == false){
		alert("Please enter a valid number with no more than two decimal places with no percent sign. (i.e. 5.5)");
		return false;
	}
}

function valid_ammount(){
	var reg = /^\$?([1-9]{1}[0-9]{0,2}(\,[0-9]{3})*(\.[0-9]{0,2})?|[1-9]{1}[0-9]{0,}(\.[0-9]{0,2})?|0(\.[0-9]{0,2})?|(\.[0-9]{1,2})?)$/;
	var value = document.getElementById("loan_ammount").value;
	if(reg.test(value) == false){
		alert("Please enter a valid dollar ammount with no more than two decimal places with no dollar sign. (i.e. 75000)");
		return false;
	}
}

function valid_term(){
	var reg = /^([1-9]|[1-9]\d|100)$/;
	var value = document.getElementById("term_length").value;
	if(reg.test(value) == false || value != 30){
		if(value != 40){
			alert("Please enter 30 or 40 years");
			return false;
		}
	}
}

function calculate(){
	if(valid_percent() != false && valid_ammount() != false && valid_term() != false){
		var answer = document.getElementById("results");
		var answer2 = document.getElementById("results2");
		var rate = document.getElementById("interest_rate").value;
		var ammount = document.getElementById("loan_ammount").value;
		var monthly = document.getElementById("monthly_payments").value;
		var term = document.getElementById("term_length").value;
		var mod_rate = document.getElementById("modified_rate").value;
		var new_monthly = document.getElementById("new_monthly");
		
		var mi = mod_rate/1200;
		var base = 1;
		var mbase = 1 + mi;
		
		for (i=0; i < term * 12; i++){ 
			base = base * mbase;
		}
		
		var mod_monthly = Math.floor(ammount * mi / ( 1 - (1/base)));
		new_monthly.value = "$" + mod_monthly;
		
		answer.value = "$" + (monthly - Math.floor(ammount * mi / ( 1 - (1/base))));
		answer2.value = "$" + (60 * (monthly - Math.floor(ammount * mi / ( 1 - (1/base)))));
		
		return false;
	}
}