A simple helper to truncate values in Handlebars based on a character count.

handlebars_truncating_helper.js

Handlebars.registerHelper('trunc', function (context, options) {

    var chars = options.hash.chars || 20;
    var result = context;

    if (context.length > chars) {
        result = result.substring(0, chars);

        if (options.hash.append) {
            result += options.hash.append;
        }
    }

    return new Handlebars.SafeString(result);
});

// Usage: foo = "abcdefghijklmnopqrstuvwxyz"
// {trunc foo chars="4" append="..."}
// Returns: abcd...