javascript - unCaught type error: cannot read property 'null' value for document.getElementByID().value; -


i trying value of input field console says cannot read property null value.i have used document.getelementbyid().value function. view source code displays values javascript variable not getting value. following code: 

 <script type="text/javascript">     function addcart(id,name,price)      {        var quantity=document.getelementbyid("quantity_"+id).value;//this line gets error              $.ajax({          type:'post',          url:'addcart.php',          data:{            item_id:id,            item_name:name,            item_quantity:quantity,            item_price:price          },          success:function(response) {            document.getelementbyid("cart").innerhtml=response;          }        });         }   </script>

i tried using jquery val() function, follows...

 <script type="text/javascript">     function addcart(id,name,price)      {      var quantity = $('#quantity_'+id).val(); //this line         $.ajax({          type:'post',          url:'addcart.php',          data:{            item_id:id,            item_name:name,            item_quantity:quantity,            item_price:price          },          success:function(response) {            document.getelementbyid("cart").innerhtml=response;          }        });         }   </script>

look html code:

 <?php while($row = mysqli_fetch_array( $fetch_customer_menu_result))        {          $item_id=$row['item_id'];          $item_name=$row['item_name'];          $item_price=$row['item_price'];                   echo '                        <div class="w3-col l8 w3-col s8">            <input class="form-control w3-left" type="number" placeholder="count" id="quantity_'.$row['item_id'].'" value="1">                  <span class="w3-right"><u>rate (each):</u></span><br>                       <span class="w3-right w3-large"><b>rs. '.$row['item_price'].'</b></span>                                                     </div>              </div>               <div class="w3-col l12 w3-center" style="margin-top: 5px">              <button type="button" class="w3-red btn form-control" onclick="addcart(\' '.$item_id.' \',\' '.$item_name.' \',\' '.$item_price.' \')" >add cart</button>            </div>          </div>        </div>';        }        ?>

uncaught type error: cannot read property 'null' value document.getelementbyid().value;

this error means document.getelementbyid() returns null pointer (i.e. can't find element looking for, returns null), , trying find value of field doesn't exist (document.getelementbyid("quantity_"+id).value becomes null.value, , null not have field named value).

why?

the reason (in case) value pass in id in addcart function incorrect. however, there few causes. follow these debugging steps:

  • make sure order of parameters same defined in function , calling (i.e. not passing in name should passing in id)

  • add line above line error: console.log("quantity_"+id) , use browser console check if text box has exactly id - if doesn't, problem.

  • make sure addcart being called when text field on screen - ensure don't delete text field , call addcart, , addcart doesn't called before element has been created.

  • make sure there not 2 functions name addcart.


Comments

Post a Comment

Popular posts from this blog

python - Operations inside variables -

this question has answer here: evaluating mathematical expression in string 12 answers i want make python script finds maximum possible output using 2 operations. problem says there syntax error @ 2nd last line, in b in there. how can fix it? x = 0 = int(input("1st number:")) c = int(input("2nd number:" )) e = int(input("3rd number:" )) in range(4): if == 0: b = "+" elif == 1: b = "-" elif == 2: b = "/" else: b = "*" j in range(4): if j == 0: d = "+" elif j == 1: d = "-" elif j == 2: d = "/" else: d = "*" k = b c d e print(k) if you're after variables e on single line, couldn...
Read more

Generic Map Parameter java -

i having lot of methods of type: public static list<eduusers> getdetails(class c, map<string, integer> params) { list<eduusers> details = null; session session = hibernateutil.getsessionfactory().opensession(); transaction tx = null; try { tx = session.begintransaction(); criteria cr = session.createcriteria(c); (map.entry<string, integer> entry : params.entryset()) { cr.add(restrictions.eq(entry.getkey(), entry.getvalue())); } details = cr.list(); tx.commit(); } catch (exception asd) { log.debug(asd.getmessage()); if (tx != null) { tx.commit(); } } { session.close(); } return details; } i trying have generic method them , have written far: public static <t> list<t> getdetails(class<t> c, class<t> b) { l...
Read more

arrays - What causes a java.lang.ArrayIndexOutOfBoundsException and how do I prevent it? -

what arrayindexoutofboundsexception mean , how rid of it? here code sample triggers exception: string[] name = {"tom", "dick", "harry"}; for(int = 0; i<=name.length; i++) { system.out.print(name[i] +'\n'); } your first port of call should documentation explains reasonably clearly: thrown indicate array has been accessed illegal index. index either negative or greater or equal size of array. so example: int[] array = new int[5]; int boom = array[10]; // throws exception as how avoid it... um, don't that. careful array indexes. one problem people run thinking arrays 1-indexed, e.g. int[] array = new int[5]; // ... populate array here ... (int index = 1; index <= array.length; index++) { system.out.println(array[index]); } that miss out first element (index 0) , throw exception when index 5. valid indexes here 0-4 inclusive. correct, idiomatic for statement here be: for (int index = 0; index <...
Read more