Using $ as a key in a JS object?

Example:

console.log(myobject['media$group']);

outputs undefined

console.log(myobject['media\$group']);

outputs expected value

What's the deal? I ran into this when using youtube's API.

EDIT:

I'm confused by many of you saying it works, so I will post more info because perhaps I'm missing something stupid.

Here's the code I'm running:

console.log(feed);
console.log(feed["media$group"]["media$thumbnail"]);

Here's the object from the first log cut\pasted from firebug:

author
    [Object { name={...}, uri={...}}]

category
    [Object { scheme="http://schemas.google.com/g/2005#kind", term="http://gdata.youtube.com/schemas/2007#video"}, Object { scheme="http://gdata.youtube.co...mas/2007/categories.cat", term="Tech", label="Science & Technology"}, Object { scheme="http://gdata.youtube.com/schemas/2007/ke开发者_如何学运维ywords.cat", term="google"}, 10 more...]

content
    Object { $t="The Google Doodle team ...googleblog.blogspot.com", type="text"}

gd$comments
    Object { gd$feedLink={...}}

gd$rating
    Object { average=4.77813, max=5, more...}

id
    Object { $t="http://gdata.youtube.co.../api/videos/3NGSU2PM9dA"}

link
    [Object { rel="alternate", type="text/html", href="http://www.youtube.com/...A&feature=youtube_gdata"}, Object { rel="http://gdata.youtube.co...as/2007#video.responses", type="application/atom+xml", href="http://gdata.youtube.co...s/3NGSU2PM9dA/responses"}, Object { rel="http://gdata.youtube.co...emas/2007#video.related", type="application/atom+xml", href="http://gdata.youtube.co...eos/3NGSU2PM9dA/related"}, 2 more...]

media$group
    Object { media$category=[1], media$content=[3], more...}

published
    Object { $t="2011-04-14T00:31:33.000Z"}

title
    Object { $t="Charlie Chaplin Google Doodle", type="text"}

updated
    Object { $t="2011-04-15T23:14:58.000Z"}

yt$statistics
    Object { favoriteCount="2539", viewCount="0"}

And here's the error from the second console.log:

feed.media is undefined
[Break On This Error] console.log(feed["media"]["media"]); 

'media\$group' and 'media$group' are equal since \$ is not a known escape sequence and thus turns into $.

So the field simply got defined between your two calls.

Your case is interesting, I don't know why you required to escape $ character with a back slash, but these are outputs as expected.

var obj = {
    some$Key: 'someValue'
}

console.log(obj.some$Key); // someValue
console.log(obj['some$Key']); // someValue

Sounds like the server escaping characters in your string. That or some other string building system has been escaping the $ character and then setting your object onto that value.

Also "foo$bar" === "foo\$bar"

It works fine.

a={'a':'test1', '$':'yes'}

console.log(a['$']); // 'yes'

Try this (jsfiddle)