New Twiddle

components.if-let.js

import Ember from 'ember';

export default Ember.Component.extend().reopenClass({
  positionalParams: ['predicate']
});

controllers.application.js

import Ember from 'ember';

export default Ember.Controller.extend({
  appName: 'Ember Twiddle'
});

templates.application.hbs

{{#if-let "Alex" as |value|}}
  {{value}} is truthy
{{else}}
  The 1st positional param was falsy
{{/if-let}}

<hr />

{{#if-let false as |value|}}
  {{value}} is truthy
{{else}}
  The 1st positional param was falsy
{{/if-let}}

templates.components.if-let.hbs

{{#if predicate}}
  {{yield predicate}}
{{else}}
  {{yield to="inverse"}}
{{/if}}

twiddle.json

{
  "version": "0.15.1",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.js",
    "ember": "3.4.3",
    "ember-template-compiler": "3.4.3",
    "ember-testing": "3.4.3"
  },
  "addons": {
    "ember-data": "3.4.2"
  }
}