Javascript没有获取属性值

Question

Thanks to help here, I got a sample piece of code working When I tried to apply it to the real thing, something is not working quite.

In my view (new.html.erb), I have the following:

<%= f.hidden_field :addtl_attendee_payment, :value => Addtl_attendee_charge %>

(Addtl_attendee_charge comes from a config file)

and in my javascript file, I have the following:

function display_value() {
    var a = $("#addtl_attendee_payment");
    alert(a.val());
}

and in another spot in my new.html.erb, I have the following:

<script><%= "display_value()" %></script>

When I run this, I get "undefined" inside the alert box. If I look at the HTML (using firefly), here's what I get:

<input id="payment_addtl_attendee_payment" type="hidden" value="500" name="payment[addtl_attendee_payment]">

Payment is the model name. This is the same type of code that worked for the test code. Any ideas?

Note:

Note again that the model name is Payment, and although I did not add payment to the attribute name, Rails added it automatically. I did try another variation on the javascript file:

function display_value() {
    var a = $("#payment_addtl_attendee_payment");
    alert(a.val());
}

But that did not work either (getting the same message). I think that adding the payment_ is normal and is done by Rails (but I could be wrong, being a newbie)

Answer 1

请注意，渲染标记中有不同的ID：

var a = $("#payment_addtl_attendee_payment");

Answer 2

Hi if your ID is fixed then you can use

 var a = $("#payment_addtl_attendee_payment");

for getting the value , or you can go with this piece of code

 var a = $("#_addtl_attendee_payment");

Answer 3

why can't you add a unique class attribute for the hidden field and access the value through it.

<%= f.hidden_field :addtl_attendee_payment, :class="some_unique_class_id", :value => Addtl_attendee_charge %>

And you can access the value as below.

function display_value() {
    var a = $(".some_unique_class_id");
    alert(a.val());
}