cache this.$()

components.my-component.js

import Ember from 'ember';

export default Ember.Component.extend({
  didInsertElement() {
    let i;
    
    console.time('a');
    const $this = this.$();
    for (i = 0 ; i < 10000 ; i++) {
     	 if ($this) {}
    }
    console.timeEnd('a');
    
    console.time('b');
    for (i = 0 ; i < 10000 ; i++) {
      if (this.$()) {}
    }
    console.timeEnd('b');
  }
});

controllers.application.js

import Ember from 'ember';

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

templates.application.hbs

<h1>Welcome to {{appName}}</h1>
<br>
<br>
{{outlet}}
{{my-component}}
<br>
<br>

templates.components.my-component.hbs

<span>2</span>

twiddle.json

{
  "version": "0.10.5",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/1.11.3/jquery.js",
    "ember": "2.8.0",
    "ember-data": "2.8.0",
    "ember-template-compiler": "2.8.0",
    "ember-testing": "2.8.0"
  },
  "addons": {}
}