Handlebars.registerHelper('link_to', function() {
  return "<a href='" + this.url + "'>" + this.body + "</a>";
})

var context = { posts: [{url: "/hello-world", body: "Hello World!"}] }
var source = "<ul>{{#posts}}<li>{{{link_to}}}</li>{{/posts}}</ul>"

var template = Handlebars.compile(source)
template(context)

<ul>
  <li><a href='/hello-world'>Hello World!</a></li>
</ul>