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Thread: little javascript help please

  1. #1
    Join Date
    Mar 2012
    Posts
    21

    little javascript help please

    Hi guys,

    I'm working on a code at the moment which is like a book shop. I want the program to allow the user to enter a book name and price then add it and after adding the books and its corresponding price, the program should calculate the total price.

    I have been working on this (so it is rough) but I think I have managed it bar one slight problem. The book name entered comes up as 'undefined' after adding to basket.
    I've played about with it but still no luck.

    Code:
    <html>
    <head>
    
    
    <script type="text/javascript">
    
    var bookname = new Array();
    var bookprice = new Array();
    
    
    
    //set functions for the book name entry
    
    function insert1(value)
    {
    bookname[bookname.length]=value;
    }
    
    
    
    //set function for the book price entry
    
    function insert2(value)
    {
    bookprice[bookprice.length]=value;
    }
    
    
    //display inserted name
    
    function showname()
    {
    var string ="<b>Book Name</b><br>";
    
    for(i = 0; i < bookname.length ; i++) 
    {
    	string = string +  bookname[i]+"<br>"; 
    }
    
    if (bookname.length)				
    {
    document.getElementById('myDiv1').innerHTML = string;				//if name is entered, show value entered on myDiv section
    }
    }
    
    
    
    //display inserted price
    
    function showprice()
    {
    var string="<b>Book Price</b><br>";
    
    for(i = 0; i < bookprice.length ; i++) 
    {
    	string = string + " " + bookprice[i]+"<br>";
    }
    
    if(bookprice.length)
    {
    document.getElementById('myDiv2').innerHTML = string;
    }
    }
    
    
    
    //set function to calculate the total price
    
    function totalprice()
    {
    var total = 0;
    for(var i = 0; i < bookprice.length; i++)
    {
    var thisvalue = parseFloat(bookprice[i]);							//decimal (allows pence cost as well (ie. 5.50))
    
    if(!isNaN(thisvalue))												//!isNaN() = returns true if value is not a number
    {
    	total += thisvalue;
    }
    }
    
    alert( "The total price is "+total.toFixed(2));				//shows price to 2 decimal places
    }
    
    
    </script>
    </head>
    
    
    <body>
    
    <h3>Book Purchase</h3>
    
    
    <!--positions for book entry-->
    
    <form name="form1">
    
    <table width="407">
    <tr>
    <td width="154" align="right"><b>Book Name</b>
    <td width="9"><b>&nbsp;:</b>
    <td width="224">
    <input type="text" name="name"/>
    </tr>
    <tr>
    <td width="154" align="right">
    <td width="9">
    <td width="224">
    </tr>
    <tr>
    <td width="154" align="right">
    <td width="9">
    <td width="224"> 
    
    
    </tr>
    </table>
    </form>
    
    <!--positions for book price-->
    
    <form name="form2">
    
    <table width="407">
    <tr>
    <td width="154" align="right"><b>Book Price :</b>
    <td width="9"><b>&nbsp;</b>
    <td width="224">
    <input type="text" name="cost"/>
    </tr>
    <tr>
    <td width="154" align="right">
    <td width="9">
    <td width="224">
    </tr>
    <tr>
    <td width="154" align="right">
    <td width="9">
    <td width="224"> 
    
    <input type="button" value="Add To Basket" onclick="insert1(this.form.name.value),showname(); insert2(this.form.cost.value),showprice();"/> 		<!--the button comprimises of two functions (show both name and price together-->
    </tr>
    
    </table>
    </form>
    
    
    <tr>
    <table width = 100% >
    <td width = 300px>
    <div id="myDiv1"></div> 
    </td>
    
    <td width = 300px>
    <div id="myDiv2"></div> 
    </td>
    <td width 80%>
    </td>
    
    </tr>
    </table>
    
    
    <br><br><input type="button" value="Total Price" onclick="totalprice();" />					<!--button to calculate the total price added-->
    
    
    <input type="button" Value="Print This Screen" onclick="window.print();"/> 						<!--button to print the window-->
    
      
    </body>
    
    </html>
    I've put in little comments to help me as I am not an expert in this field and make it simpler for myself!
    Can anybody suggest how I may solve this problem?

    Any help is much appreciated!

  2. #2
    Join Date
    Feb 2012
    Location
    youTUBE
    Posts
    234
    When this is used in the context of the button
    Code:
     
    <input id="butonID" type="button" value="Add To Basket" onclick="insert1(this.form.name.value),showname(); insert2(this.form.cost.value),showprice();"/> <!--the button comprimises of two functions (show both name and price together-->
    it is the same as writing
    Code:
     
    myTHIS=document.getElementById('buttonID');
    //so (this==myTHIS).
    The implication is form is not a child of this, unlike
    Code:
     
    this.style='color:purple';

  3. #3
    Join Date
    Nov 2010
    Posts
    1,083


    there's nothing wrong with referring to a form as this.form, in fact it is a much more efficient way to access the form, rather than document.forms[0]... or document.myform...

    but the button and the target element have to be in the same form

    otherwise you will run into problems. undefined problems

  4. #4
    Join Date
    Mar 2012
    Posts
    21
    I still don't understand :S so which part/line would you recommend to delete?

    sorrrry to be a pain, but I'm just having a hard time trying to get this whole JavaScript process in my head.

  5. #5
    Join Date
    Nov 2010
    Posts
    1,083
    for it to work you need for everything to be in the one form. you currently have two - which is why one variable is accessed and the other comes up undefined

  6. #6
    Join Date
    Mar 2012
    Posts
    21

    Smile

    Thanks a lot! Its worked now.
    It's those small things you fail to notice ha, last time I did a program a simple "}" was missing and I was pulling my hair out trying to fix it!



    Once again thanks, much appreciated!

  7. #7
    Join Date
    Nov 2010
    Posts
    1,083
    Quote Originally Posted by jamesy23 View Post
    It's those small things you fail to notice ha, last time I did a program a simple "}" was missing and I was pulling my hair out trying to fix it!
    yet another reason to learn how to use a debugger.

    gald you got it working

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