difference between return true; and return false;

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  • w i l l
    #1

    difference between return true; and return false;

    Why does this work the way it does?
    If someone could explain return true, and return false to me I'd
    greatly appreciate it.

    <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">

    <html>
    <head>
    <title>Form.htm l</title>
    </head>

    <body>
    <script language="JavaS cript">
    function form1_onsubmit( ) {
    var returnValue = false;
    if (document.form1 .txtName.value == "") {
    alert("Please Enter your Name");
    document.form1. txtName.focus() ;
    }
    else {
    returnValue = true;
    }
    return returnValue;
    }
    </script>

    <form action="formhan dler.asp" method="post" name="form1" onSubmit="
    return form1_onsubmit( )">
    name: <input type="text" name="txtName">
    <input type="submit" value="Go">

    </form>

    </body>
    </html>


    w i l l
    Tags: javascript+returntrue, return true
    • Gareth Church
      #2
      Re: difference between return true; and return false;

      "w i l l" <willis_31_40@y ahoo.com> wrote in message
      news:93hbgvg9o7 sdlssthh7qtrq8g p23rk2uft@4ax.c om...[color=blue]
      > Why does this work the way it does?
      > If someone could explain return true, and return false to me I'd
      > greatly appreciate it.[/color]

      When you return something from a function, that value gets returned to the
      caller. For instance, say I had a method to multiply two numbers. Maybe the
      code looks like this:

      function multiply(num1, num2) {
      return num1 * num2;
      }
      result = multiply(2, 4);

      The function multiply will return the result of it's multiplication to
      wherever it was called. The right-hand side of the result assignment is
      where the function is called, so that is where the result is returned to.
      So, in this case (with the parameters 2 and 4), it is the same as writing
      result = 8;

      When you are using return true or false with markup, you are indicating
      whether or not you want the default action to happen after the javascript
      has been executed. An example is needed:

      <a href="somepage. html" onClick="alert( 'Hi'); return true;">Click Me</a>

      When the link is clicked the javascript code for the onClick will run first,
      and we get an alert. We have used return true, so that is saying when we
      click OK to remove the alert, we do want to run the markup. So in this case
      once we click OK to dismiss the alert, we would then be taken to
      somepage.html. If we changed that to return false we would get the alert,
      but wouldn't go to somepage.html.

      So in your example if the method (form1_onsubmit ) returns false, the default
      behaviour of the form (action=formhan dler.asp) won't run. In other words we
      get the alert (thrown from inside the method), and when we click ok nothing
      happens. If that method returns true though, the default behaviour will
      occur, so the form will be submitted to the asp file.

      Gareth


        Comment

        • Bagbourne
          #3
          Re: difference between return true; and return false;

          "w i l l" <willis_31_40@y ahoo.com> wrote in message
          news:93hbgvg9o7 sdlssthh7qtrq8g p23rk2uft@4ax.c om...[color=blue]
          > Why does this work the way it does?
          > If someone could explain return true, and return false to me I'd
          > greatly appreciate it.[/color]

          In a onxxxxx method where there is usually some form of standard processing
          by the browser, it's just a way of specifying whether further standard
          processing should take place.

          Returning false means no, returning true means yes. So that example aborted
          the submit if the user hasn't entered their name.

          Nige


            Comment

            • w i l l
              #4
              Re: difference between return true; and return false;

              On Sat, 5 Jul 2003 04:49:02 +1000, "Gareth Church"
              <gechurch@bigpo nd.com.au> wrote:
              [color=blue]
              >"w i l l" <willis_31_40@y ahoo.com> wrote in message
              >news:93hbgvg9o 7sdlssthh7qtrq8 gp23rk2uft@4ax. com...[color=green]
              >> Why does this work the way it does?
              >> If someone could explain return true, and return false to me I'd
              >> greatly appreciate it.[/color]
              >
              >When you return something from a function, that value gets returned to the
              >caller. For instance, say I had a method to multiply two numbers. Maybe the
              >code looks like this:
              >
              >function multiply(num1, num2) {
              > return num1 * num2;
              >}
              >result = multiply(2, 4);
              >
              >The function multiply will return the result of it's multiplication to
              >wherever it was called. The right-hand side of the result assignment is
              >where the function is called, so that is where the result is returned to.
              >So, in this case (with the parameters 2 and 4), it is the same as writing
              >result = 8;
              >
              >When you are using return true or false with markup, you are indicating
              >whether or not you want the default action to happen after the javascript
              >has been executed. An example is needed:
              >
              ><a href="somepage. html" onClick="alert( 'Hi'); return true;">Click Me</a>
              >
              >When the link is clicked the javascript code for the onClick will run first,
              >and we get an alert. We have used return true, so that is saying when we
              >click OK to remove the alert, we do want to run the markup. So in this case
              >once we click OK to dismiss the alert, we would then be taken to
              >somepage.htm l. If we changed that to return false we would get the alert,
              >but wouldn't go to somepage.html.
              >
              >So in your example if the method (form1_onsubmit ) returns false, the default
              >behaviour of the form (action=formhan dler.asp) won't run. In other words we
              >get the alert (thrown from inside the method), and when we click ok nothing
              >happens. If that method returns true though, the default behaviour will
              >occur, so the form will be submitted to the asp file.
              >
              >Gareth
              >[/color]


              Excellent explination, Thanks!

                Comment

                • Dan Brussee
                  #5
                  Re: difference between return true; and return false;

                  In article <93hbgvg9o7sdls sthh7qtrq8gp23r k2uft@4ax.com>, willis_31_40
                  @yahoo.com says...[color=blue]
                  > Why does this work the way it does?
                  > If someone could explain return true, and return false to me I'd
                  > greatly appreciate it.
                  >[/color]

                  It's a boolean thing - you wouldnt understand.

                  Just kidding :)


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                  Remove NOT from email address to reply. AntiSpam in action.

                    Comment

                    • Dan Brussee
                      #6
                      Re: difference between return true; and return false;

                      In article <93hbgvg9o7sdls sthh7qtrq8gp23r k2uft@4ax.com>, willis_31_40
                      @yahoo.com says...[color=blue]
                      > Why does this work the way it does?
                      > If someone could explain return true, and return false to me I'd
                      > greatly appreciate it.
                      >[/color]

                      Or better yet...

                      function understand() {
                      return false;
                      }


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                        Comment

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