function getElementsByClassName(classname, node) {
  
      if(!node) node = document.getElementsByTagName("body")[0];
   
      var a = [];
   
      var re = new RegExp('\\b' + classname + '\\b');
   
      var els = node.getElementsByTagName("*");
   
      for(var i=0,j=els.length; i<j; i++)
   
      if(re.test(els[i].className))a.push(els[i]);
   
      return a;
   
}

function show_letter(id){
	var c = getElementsByClassName('clicked_letter');
	if(c[0]) {
		var el = c[0];
		el.className = '';}
	var a = getElementsByClassName('visited_letter');
	for (var i=0;i<a.length;i++){
		var ela = a[i];	
		ela.style.display = 'none';
				}
	document.getElementById(id).style.display = 'block';
	document.getElementById('show_'+id).className = 'clicked_letter';
}

function val(field)  {

var valid = '0123456789,.';

var ok = 'yes';
var temp;
for (var i=0; i<field.value.length; i++) {
    temp = '' + field.value.substring(i, i+1);
    if (valid.indexOf(temp) == '-1') ok = 'no';
}

if (ok == 'no') {
    alert('Numerical values only please');
    field.value=field.value.substring(0,field.value.length-1);
    field.focus();

   }

}


function get_val(id) {
    var elem = (document.getElementById(id).value);
    return Number(elem);
}


function calculate() {
    var sum = get_val('proposed_rent')+get_val('phone_bill')+get_val('creditcard_loan_repayments')+get_val('tv_licence')+get_val('council_tax')+get_val('gas_and_electric')+get_val('travel')+get_val('other')+get_val('food_and_drink');
    var rem = get_val('monthly_income')-sum;

    document.getElementById('total_outgoings').value = sum;

    if ( rem < 0 ) {
        document.getElementById('disposable_income').style.color='#ff0000';
        document.getElementById('disposable_income').value = rem;
    }
    else  {
        document.getElementById('disposable_income').style.color='#000000';
        document.getElementById('disposable_income').value = rem;
    }
}