adds $index property to nested templates

[clarkbox]

(similar to the each tag) adds an "$index" property to the data item passed to nested templates using the {{tmpl}} tag
fixes: https://github.com/jquery/jquery-tmpl/issues#issue/28

[clarkbox]

hmmmm.... $index is only available when an array has been passed to the template. If a dev creates a template to be used against an array AND single object, and does not handle the undefined case (of $index), the template will break.

Should $index always be set?

[BorisMoore]

We decided against this feature for the reasons explained here:
http://api.jquery.com/jquery.tmpl/#comment-111707270
http://api.jquery.com/jquery.tmpl/#comment-98013066

Keeping issue 28 open though, to track this request.

[clarkbox]

you can break the index of an {{each}} the same way as pointed to in above links - by manipulating the dom. but i do get your point. there are differences in the implied ways to use {{tmpl}} and {{each}} tag, it could be much more common to reuse a template and insert in dom without an update().

i admit, it did not occur to me to use the $.inArray approach to get the index from the parent. one problem would be performance in large data sets. i also found in my scenario that i could not use the $.inArray approach, as i was only using templates to setup the initial render, and manipulate the dom from then on - NOT keeping my bound object in sync. but thats just my narrow scenario. I happen to not care about the actual index after initial render as well.

[BorisMoore]

Perf is an important aspect too, I agree. I'll be on the lookout for alternatives to address this issue. One way good be to pass the index to the rendered event, so users can easily set index on the item if they want to, in the onRendered handler.

[BorisMoore]

This is a dup of http://github.com/jquery/jquery-tmpl/issues#issue/28