pass variable from html to javascript

Question

<%= semantic_form_for :.........  do |f| %>
<%= f.inputs do%>
    <%= pluralize @size, 'Profitable Routes to test'%>
    <p>User id: <%= @id %><p>
    ....

<title> audio player</title>
    <meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1" />
    <link href="/skin/pink.flag/jplayer.pink.flag.css" rel="stylesheet" type="text/css" />

    <script type="text/javascript">
    $(document).ready(function(){
        var u_id = document.getElementById('id')
        $("#jquery_jplayer_1").jPlayer({
            ......
                ......
                ......
                .......
        });
    });
        //]]>
    </script>

I want to pass the User id to javascript, i'm trying to do it with this: var u_id = document.getElementById('id') but it says that u_id is null, who can i pass it? Thanks!

document.getElementById('id') will give you the DOM element that has the ID id, not the actual element ID — letiagoalves
– letiagoalves, Commented Mar 13, 2013 at 13:43
In the event the script is going to be properly separated into a file and referenced in a script tag within the header, write your required data either into a hidden field or into an elements data attribute. That way you can use just the script to access what you need instead of hacky inline-script. If the hidden field is for example has an id of "userId" you can then do something similar to $("#userId").val() to get the user id. — Nope
– Nope, Commented Mar 13, 2013 at 13:56

maxdec · Accepted Answer · 2013-03-13 13:54:17Z

4

You should write the variable directly in the JavaScript code:

var u_id = <%= @id %>;

Actually when you use document.getElementById() in JavaScript you get a DOM element. And not the variable @id. The variable @id doesn't event exist for JavaScript.

Why?

I guess you're using Rails. @id is a Rails variable. Rails compiles the templates (on the server) before sending the final html page to the user. It means it replaces all the <% %> by the results of each block which are plain text.

The JavaScript is then run on the client browser. It's not aware of Rails.

When you do var u_id = <%= @id %>; Rails compiles it in something like var u_id = 198297; which is send to the client browser. Then JavaScript is happy, the variable is correctly set.

edited Mar 13, 2013 at 13:54

answered Mar 13, 2013 at 13:43

maxdec

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3 Comments

Nope Over a year ago

Not sure about the exact syntax but would using <input type="hidden" id="userId" value=@id/> in the page and var userId =$("#userId").val() in the script file not work too and keep the layers separated? I'm assuming this for a flexible solution where the script might not be embedded in the page but instead is in a separate file.

maxdec Over a year ago

Should work. But you can as well use the JavaScript global scope, just define the variable in this page with <script>var u_id = <%= @id %>;</script> and use the u_id variable everywhere else in JavaScript, even separate files. I wouldn't add an html field just for this purpose.

JHBonarius Over a year ago

@Nope imho your comment is answer worthy... I'd give you a +1. I'm maintaining a prog and due to security settings I'm not allowed to execute in-age scripts. Your suggestion works for me.

Nick Andriopoulos · Accepted Answer · 2013-03-13 13:43:20Z

0

document.getElementById('id') is the element, not its value. You should use something similar to

id = document.getElementById('id').innerHTML;

answered Mar 13, 2013 at 13:43

Nick Andriopoulos

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Comments

Masoud Aghaei · Accepted Answer · 2013-03-13 13:43:36Z

0

u_id is the dom element . you should select a attr of this element

u_id.value

or

u_id.innerHTML

in jquery :

u_id.val()
u_id.html()

answered Mar 13, 2013 at 13:43

Masoud Aghaei

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1 Comment

Anthony Grist Over a year ago

That's not going to help if u_id is undefined because there's no element with an id of 'id'; trying to access a property of it would throw an error.

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