invalid return error...calling function?

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  • evan.cooch@NOSPAMcornell.edu
    #1

    invalid return error...calling function?

    Greetings.

    Suppose I have some function called "CheckIt" - some function to
    validate form data before submitting it to e CGI script. Pretend the
    name of the form is "TheForm".

    If I use the following code, everything work perfctly:

    <Input type=button VALUE="Submit your form"
    onClick="javasc ript:return CheckIt(TheForm )">

    But, if I try to associate the submission with a graphic (call it
    "submit_botton. gif"), using the following, I get an error:

    <a href="javascrip t:return CheckIt(AbsForm )">
    <img src="images/submit_button.g if" border=0></a>


    the error message I get is:

    "invalid return"

    Using the Javascript console in Mozilla, it points to line 1, which is
    indicated to be

    javascript:retu rn CheckIt(AbsForm )


    I've tried several things, to no avail. I'm puzzled, because I've used
    similar approaches (to associating functions with images), without any
    problems.

    Any suggestions? Pointers to the "obvious mistake"? :-)

    Thanks in advance...
    Tags: None
    • Lee
      #2
      Re: invalid return error...calling function?

      evan.cooch@NOSP AMcornell.edu said:[color=blue]
      >
      >Greetings.
      >
      >Suppose I have some function called "CheckIt" - some function to
      >validate form data before submitting it to e CGI script. Pretend the
      >name of the form is "TheForm".
      >
      >If I use the following code, everything work perfctly:
      >
      ><Input type=button VALUE="Submit your form"
      >onClick="javas cript:return CheckIt(TheForm )">
      >
      >But, if I try to associate the submission with a graphic (call it
      >"submit_botton .gif"), using the following, I get an error:
      >
      ><a href="javascrip t:return CheckIt(AbsForm )">
      ><img src="images/submit_button.g if" border=0></a>
      >
      >
      >the error message I get is:
      >
      >"invalid return"[/color]

      There is a major difference between the value of an onclick attribute
      and the value of an href attribute. The onclick attribute is expected
      to be executable code.
      The token "javascript :", if present, is read as either a language
      specification or as a label, depending on what the browser is expecting.

      On the other hand, the href attribute is supposed to be an URI.
      The token "javascript :", if present, is read as a protocol name.

      The javascript [pseudo]protocol means that the browser should evaluate
      the javascript expression following the colon, and use its value as
      the new contents of the page, as in:

      href="javascrip t:'<html><body> '+(new Date()).toLocal eString()+'</body></html>'"

      Whatever value you're returning isn't valid HTML (or void, which means
      to leave the current page unchanged).

      In general, don't use the javascript: protocol. Use the onclick event
      handler of the link, and return false, so the link isn't followed.

      You should also investigate these concepts:
      onSubmit
      input type="submit"
      input type="image"

        Comment

        • evan.cooch@NOSPAMcornell.edu
          #3
          Re: invalid return error...calling function?

          THanks very much!

          My followup embedded below:

          [color=blue]
          >There is a major difference between the value of an onclick attribute
          >and the value of an href attribute. The onclick attribute is expected
          >to be executable code.
          >The token "javascript :", if present, is read as either a language
          >specificatio n or as a label, depending on what the browser is expecting.
          >
          >On the other hand, the href attribute is supposed to be an URI.
          >The token "javascript :", if present, is read as a protocol name.
          >
          >The javascript [pseudo]protocol means that the browser should evaluate
          >the javascript expression following the colon, and use its value as
          >the new contents of the page, as in:
          >
          >href="javascri pt:'<html><body >'+(new Date()).toLocal eString()+'</body></html>'"
          >
          >Whatever value you're returning isn't valid HTML (or void, which means
          >to leave the current page unchanged).[/color]

          OK, so why then DOES the following worK

          <a href="javascrip t:void(document .TheForm.reset( ))">
          <img src="images/start_over.gif" ></a>

          It uses href, but it executes the javascript just as intended.

          [color=blue]
          >
          >In general, don't use the javascript: protocol. Use the onclick event
          >handler of the link, and return false, so the link isn't followed.
          >
          >You should also investigate these concepts:
          >onSubmit
          >input type="submit"
          >input type="image"[/color]


          I'll do that, but would be interested in your answer to why the href
          approach works in some cases, but not others.

            Comment

            • Lee
              #4
              Re: invalid return error...calling function?

              evan.cooch@NOSP AMcornell.edu said:[color=blue]
              >
              >THanks very much!
              >
              >My followup embedded below:
              >
              >[color=green]
              >>There is a major difference between the value of an onclick attribute
              >>and the value of an href attribute. The onclick attribute is expected
              >>to be executable code.
              >>The token "javascript :", if present, is read as either a language
              >>specificati on or as a label, depending on what the browser is expecting.
              >>
              >>On the other hand, the href attribute is supposed to be an URI.
              >>The token "javascript :", if present, is read as a protocol name.
              >>
              >>The javascript [pseudo]protocol means that the browser should evaluate
              >>the javascript expression following the colon, and use its value as
              >>the new contents of the page, as in:
              >>
              >>href="javascr ipt:'<html><bod y>'+(new Date()).toLocal eString()+'</body></html>'"
              >>
              >>Whatever value you're returning isn't valid HTML (or void, which means
              >>to leave the current page unchanged).[/color]
              >
              >OK, so why then DOES the following worK
              >
              ><a href="javascrip t:void(document .TheForm.reset( ))">
              ><img src="images/start_over.gif" ></a>
              >
              >It uses href, but it executes the javascript just as intended.[/color]

              Because the Javascript expression evaluates to void, which means to
              leave the current page unchanged.

                Comment

                • evan.cooch@NOSPAMcornell.edu
                  #5
                  Re: invalid return error...calling function?

                  [color=blue][color=green]
                  >>OK, so why then DOES the following worK
                  >>
                  >><a href="javascrip t:void(document .TheForm.reset( ))">
                  >><img src="images/start_over.gif" ></a>
                  >>
                  >>It uses href, but it executes the javascript just as intended.[/color]
                  >
                  >Because the Javascript expression evaluates to void, which means to
                  >leave the current page unchanged.[/color]


                  Got it - thanks....

                    Comment

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