How to read additional data within handlebars block expression template?

Question

My html document will have div container which gets populated with handlebars template name 'relatedVideosTemplate' on execution.

<div id="relVideos"></div>

Below anonymous function will make ajax request and pass the data to handlebar template which loops over all items in data object to construct related videos UI.

(function(options) {
    var defualt = {
        defaultThumb: "/url/to/default/thumbnail/",
        apiURL: '/path/to/api/url'
    };

    options = options || {};
    options = $.extend(true, defaults, options);               

    // handlebars template for the related video carousel
    var relatedVideosTemplate : "<h3>Related Videos</h3>" +
                            "<ul class=\"related-videos\">" +
                            "{{#foreach items}}<li class=\"video {{#if $last}} last{{/if}}\">" +
                            "<a href=\"/video/?videoid={{id}}\" class=\"image\">" +
                            "<img alt=\"{{name}}\" {{#if videoStillURL}}src=\"{{videoStillURL}}\"{{else}}src=\"{{defaultVideoThumb}}\"{{/if}} width=\"90\" height=\"75\" data-id=\"{{id}}\"  onerror=\"this.src='{{defaultVideoThumb}}';\" />" +
                            "<span class=\"video-time\">{{length}}</span></a>" +
                            "<div class=\"info\"><h5><a href=\"/video/?videoid={{id}}\">{{name}}</a></h5>" +
                            "<span class=\"published-date\">{{publishedDate}}</span>" + 
                            "{{#if playsTotal}}<span class=\"video-views\">{{playsTotal}} views</span>{{/if}}" +                                
                            "</div></li>{{/foreach}}" +
                            "</ul>",
         template, relVideosHTML;           


    $.ajax({
        url: options.apiURL,
        success: function(data) {
            template = Handlebars.compile(relatedVideosTemplate);
            relVideosHTML = template(data);
            $("#relVideos").html( relVideosHTML );  
        }               
    }); 
});

Its very likely the video still image (thumbnail) for some videos will return 404 and in that case I use onerror event on image tag to replace it with default thumbnail.

Is there a way to pass this default thumbnal value as object to handlebars block expression template ?

I don't want to amend the data object to have 'defaultThumb' property for all items. Like below...

for ( i = 0, max = data.items.length; i < max; i++) {
    // Adding new property to each item in data object
    data.items[i].defaultThumb = options.defaultThumb;
};

It seems to me amending data property in above loop is non efficient as the defaultThumb is same across all videos which return 404 for still(thumb) image.

Answer 1

Why not set defaultVideoThumb once at the top level and then reference it as {{../defaultVideoThumb}} inside the loop? Something like this in the template:

<img
    {{#if videoStillURL}}src="{{videoStillURL}}"{{else}}src="{{../defaultVideoThumb}}"{{/if}}
    width="90" height="75"
    onerror="this.src='{{../defaultVideoThumb}}'
>

and then in the JavaScript:

data.defaultVideoThumb = '...';
var html = template(data);

Demo: http://jsfiddle.net/ambiguous/9ecx3/