Have two text fields react to each other

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October 26th, 2005, 08:44 AM

roggel

Contributing User

Join Date: Apr 2007

Location: The Netherlands

Posts: 9

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Have two text fields react to each other

Hi there,

I'm building a stock market game, where children can buy and sell shares in virtual companies.
At some point I want them to be able to buy shares, obviously. On the buy page there should be two textfields, A and B.
The children can now decide to type in the NUMBER of shares they want to buy in textfield A. When they press Tab or Enter, textfield B should automatically update to the amount of dollars they should pay for it (number of shares * value of 1 share).
But they should also be able to type in the amount of dollars they want to spend in textfield B, which would automatically update textfield A to the number of shares they'd get for that amount of money.

Can this be done using PHP? (I guess not, but I thought I should ask). Should this be done in JavaScript and if so, how? (Complete Javascript newbie)...

October 28th, 2005, 03:48 AM

brut

Join Date: Apr 2007

Posts: 367

Time spent in forums: 3 m 30 sec
Reputation Power: 2

RE: Have two text fields react to each other

Something like this should get you started:

php Code:

Original - php Code

 
  <script language="javascript">
      function update(obj){
         stockPrice=document.getElementById('stock').option  s[document.getElementById('stock').selectedIndex].value;
         if(obj.id=="shares"){
            document.getElementById('cost').value=obj.value*st  ockPrice;
         }else{
            document.getElementById('shares').value=obj.value/stockPrice;
         }
      }
  </script>
 
  <select name="stock" id="stock">
   <option value="47.4">DIS</option>
   <option value="82.1">TWX</option>
   <option value="49.3">VIA-B</option>
   <option value="47.4">NWS-A</option>
  </select>
  <br />
  Shares:<input type="text> name="shares" id="shares" onchange="update(this);">
  <br />
  Cost:<input type="text> name="cost" id="cost" onchange="update(this);">

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