experiment-helper

controllers.application.js

import Ember from 'ember';

export default Ember.Controller.extend({
  appName: 'Ember Twiddle',
  imageURL: 'img/test.png',
  styles: {
   height: '300px',
   'background-image': 'url(img/test.png)',
  }
});

helpers.my-helper.js

import Ember from 'ember';
import { htmlSafe } from '@ember/string';

const GLUE = ':';
const SEPARATOR = ';';

function joinStyles(styles) {
  return Object.keys(styles)
    .map(style => `${style}${GLUE}${styles[style]}`)
    .join(SEPARATOR);
}

export function myHelper(params, hash) {
  const styles = joinStyles(hash);
  return htmlSafe(styles);
}

export default Ember.Helper.helper(myHelper);

helpers.my-other-helper.js

import Ember from 'ember';

const GLUE = '=';
const SEPARATOR = ' ';

function joinParams(params) {
  return Object.keys(params)
    .map(param => `${param}${GLUE}${params[param]}`)
    
}

export function myOtherHelper(params) {
  const obj = params[0];
  console.log(joinParams(obj))
  
  return joinParams(obj);
}

export default Ember.Helper.helper(myOtherHelper);

templates.application.hbs

<h1>Welcome to {{appName}}</h1>
<br>
<br>
{{outlet}}
<br>
<br>

{{my-helper height='300px' background-image=(concat 'url(' imageURL ')')}}
<br/>
{{log styles}}
<br/>
{{my-helper (my-other-helper styles)}}

twiddle.json

{
  "version": "0.15.0",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.js",
    "ember": "3.2.2",
    "ember-template-compiler": "3.2.2",
    "ember-testing": "3.2.2"
  },
  "addons": {
    "ember-data": "3.2.0"
  }
}