无法将变量移出要使用的函数

Question

I am really struggling with this. I have created a form which calculates what the person owes based on how many people in a tent and if they are paying by credit card. The amounts update depending on the selection. When the user submits they should be redirected to PayPal with the total amount on the end of the url, Ie:

PayPal.me/240 for £240 or PayPal.me/600 for £600

The issue is my price variable is outside of my other function which sets the redirect, and the price amount never makes it to the redirect.

This is what I have tried:

HTML:

    <select name='field_0' id='field_0' class='text_select' onchange="pricecalc()"   >  
<option value="2 people" >2 people</option> 
<option value="3 people" >3 people</option> 
<option value="4 people" >4 people</option> 
<option value="5 people" >5 people</option> 
<option value="6 people" >6 people</option> 
</select>

    <select name='field_1' id='field_1' class='text_select' onchange="pricecalc()"   >  
<option value="Bank transfer" >Bank transfer</option>   
<option value="Debit card" >Debit card</option> 
<option value="Credit card + 3.4%" >Credit card + 3.4%</option> 
</select>         
<b>Total Price</b>
<span id="cost">Hello World!</span>
<b>Price Each</b>
<span id="costeach">Hello World!</span>

Relevant JS:

var myprice;
function pricecalc() {
  var a = document.getElementById("field_0");
  var quantity = a.value.substring(0, 1);
  var b = document.getElementById("field_1");
  var type = b.value;

  if (quantity == '2') {
    var rate = '120';
  } else if (quantity == '3') {
    var rate = '110';
  } else {
    var rate = '100';
  }

  myprice = rate * quantity;
  if (type == 'Credit card + 3.4%') {
    myprice = myprice * 1.034;
  }

  var price_each = (myprice / quantity);
  document.getElementById("cost").innerHTML = myprice;
  document.getElementById("costeach").innerHTML = price_each;
}

function PHPFMG( formID ){
    var redirect = 'https://www.paypal.me/tim/' + myprice;

Answer 1

I would recommend doing this instead

function pricecalc() {
  var myprice;
  var a = document.getElementById("field_0");
  var quantity = a.value.substring(0, 1);
  var b = document.getElementById("field_1");
  var type = b.value;

  if (quantity == '2') {
    var rate = '120';
  } else if (quantity == '3') {
    var rate = '110';
  } else {
    var rate = '100';
  }

  myprice = rate * quantity;
  if (type == 'Credit card + 3.4%') {
    myprice = myprice * 1.034;
  }

  var price_each = (myprice / quantity);
  document.getElementById("cost").innerHTML = myprice;
  document.getElementById("costeach").innerHTML = price_each;

  return myprice;
}

Then

function PHPFMG( formID ){
    var myprice = pricecalc();
    var redirect = 'https://www.paypal.me/tim/' + myprice;
}

This way you don't polute the global scope