未选择下拉列表中的默认值

Question

I have a drop down list [ Incident, Question, Problem, Task]. I have written a code when an end user logins in and has a tag called product the default value should be problem. However it does not seem to work. It still gives the user the option to select values from the list.

$j(document).ready(function() {  
if(location.pathname == '/requests/new') {
var ct = currentUser.tags;

 if(ct.indexOf("product") >= 0){
 $j(document.getElementById("ticket_fields_75389").value = "Problem"); 
  }
 else {
 $j(document.getElementById("ticket_fields_75389").value = "");
 } 

 }
 })

Answer 1

Note: This answer is incorrect. I will delete it once I know the OP read my comment.

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It still gives the user the option to select values from the list.

Well, of course, setting value will only change the initially selected value. If you want "fix" the value of the select element, so that the user cannot change it, you have to make it read-only . Lets stick with jQuery (what you have is a weird mix of DOM API and jQuery ^† ):

$j("#ticket_fields_75389").val("Problem").prop('readonly', true);

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†: Let's have a close look at the line

$j(document.getElementById("ticket_fields_75389").value = "Problem");

What exactly is happening here? Obviously we have a function call ( $j(...) ) and we pass something to it. This "something" is the result of the expression

document.getElementById("ticket_fields_75389").value = "Problem"

This finds an element by ID and assigns the string "Problem" to the value property. This is an assignment expression . The result of an assignment expression is the assigned value, ie "Problem" .

That is the value that is passed to $j(...) , so we have $j("Problem"); . Since $j refers to jQuery , this would search for all elements with tag name Problem , which does not exist in HTML. It would also return a jQuery object, but you are not doing anything with it.

Hence the wrapping in $j(...) is completely unnecessary or even wrong, even though it doesn't throw a syntax or runtime error.