Emblem.js is an ember friendly templating engine used as an alternative for handlebars.js.
Emblem.js doesn't have any official plugins for emacs. However, they recommend using slim-mode plugins as they are similar.
You get slim-mode from melpa. Install with
M-x install-package slim-mode
Now we have to activate slim-mode for emblem files which will be ending with
.em or .emblem. We can use auto-mode-alist to set major modes that need to activate for files with specific extension.(add-to-list 'auto-mode-alist '("\\.\\(em\\|emblem\\)\\'" . slim-mode))
We can add this to emacs configuration which automatically activates slim mode for emblem.js files.