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  1. #1
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    Custom error for Javascript calc

    I have a temperature calculator using javascript and i need to display a custom error message the pops up when there are errors during the conversion process. The jsp page should expect and use a query string parameter named "msg" containing the error message to be reported to the user. It should be displayed when necessary as a redirect from "convert.jsp".

    here is my calculator code :

    Code:
    <!doctype html>
    <html>
      <head>
        <meta charset="UTF-8"/>
        <title>JSP Temperature Calculator</title>
      <head>
      <body>
        <h1>Temperature Conversion</h1>
        <p>
          <input type="text" id="temperature" />
          <input type="button" id="f_to_c" value="F to C" />
          <input type="button" id="c_to_f" value="C to F" />
        </p>
        <p id="result"></p>
        <script src="convert.js"></script>
      </body>
    </html>
    and here is the jsp formula for the conversion. "aka my convert.jsp page"

    Code:
    var report = function (celsius, fahrenheit) {
        document.getElementById("result").innerHTML =
            celsius + "\xb0C = " + fahrenheit + "\xb0F";
    };
    
    document.getElementById("f_to_c").onclick = function () {
        var f = document.getElementById("temperature").value;
        report((f - 32) / 1.8, f);
    };
    
    document.getElementById("c_to_f").onclick = function () {
        var c = document.getElementById("temperature").value;
        report(c, 1.8 * c + 32);
    };
    Thank you for any input.

  • #2
    Senior Coder DanInMa's Avatar
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    Ive never used jsp, but heres a start (looks like regular ole javascript to me)
    Code:
    var report = function (celsius, fahrenheit) {
    try
      {
          document.getElementById("result").innerHTML =
            celsius + "\xb0C = " + fahrenheit + "\xb0F";
      }
    catch(err)
      {
      txt="There was an error on this page.\n\n";
      txt+="Error description: " + err.message + "\n\n";
      txt+="Click OK to continue.\n\n";
      alert(txt);
      }
    };
    Last edited by DanInMa; 10-13-2013 at 02:43 AM.

  • #3
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    awesome. thank you for the help!

  • #4
    Senior Coder Dormilich's Avatar
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    Quote Originally Posted by DanInMa View Post
    (looks like regular ole javascript to me)
    that’s because it is JavaScript.
    The computer is always right. The computer is always right. The computer is always right. Take it from someone who has programmed for over ten years: not once has the computational mechanism of the machine malfunctioned.
    André Behrens, NY Times Software Developer

  • #5
    Supreme Master coder! glenngv's Avatar
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    Quote Originally Posted by DanInMa View Post
    Ive never used jsp, but heres a start (looks like regular ole javascript to me)
    Code:
    var report = function (celsius, fahrenheit) {
    try
      {
          document.getElementById("result").innerHTML =
            celsius + "\xb0C = " + fahrenheit + "\xb0F";
      }
    catch(err)
      {
      txt="There was an error on this page.\n\n";
      txt+="Error description: " + err.message + "\n\n";
      txt+="Click OK to continue.\n\n";
      alert(txt);
      }
    };
    That will only throw exception when the element with id="result" does not exist and not when there is a conversion error.

    I don't see any conversion error occurring except when the inputs are not numbers. And in that case, you would just check using isNaN() to validate the inputs without using try/catch statement.


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