Custom Handlebar Helpers used in Open Event Frontend
In Open Event Frontend, we are using custom handlebars like ‘confirm’, ‘css’, ‘includes’, ‘sanitize’, ‘text-color’, etc. Custom helpers are used to format any quantity for example ‘capitalizing the first letter of a word’, ‘reducing a number’s fractional part’, ‘making a text bold’, etc. Thus, with the help of Custom Helpers we can avoid manipulating data in controllers. We use Custom Helpers in the Handlebars’ braces before the property to be formatted. In this blog, I will be explaining one of the custom helpers used in Open Event Frontend.
Creation of custom helper :
Since ember provides an efficient and easy way to create components, controllers, routes through it’s ember-cli, we can also create helpers through a single command.
ember g helper url-encode
This will generate a helper in our app i.e two files. First one url-encode.js where all of our logic goes for helper and the other one url-encode-test.js where the tests for it are written.
Following are the two files you are going to see once you run above commands.
import Ember from 'ember';
const { Helper } = Ember;
export function urlEncode(params) {
}
export default Helper.helper(urlEncode);
url-encode.js
import { test } from 'ember-qunit';
import moduleForComponent from 'open-event-frontend/tests/helpers/component-helper';
import hbs from 'htmlbars-inline-precompile';
moduleForComponent('url-encode', 'helper:url-encode');
test('it renders', function(assert) {
this.set('inputValue', 'hello world');
this.render(hbs`{{url-encode inputValue}}`);
assert.equal(this.$().text().trim(), 'hello%20world');
});
url-encode-test.js
Now all the logic for the helper goes in url-encode.js. But before that, we pass the helper in the template and pass the params to the url-encode.js to process the data and return it.
Use in template:
<a target="_blank" rel="noopener noreferrer" href="https://www.facebook.com/sharer.php?u={{url-encode event.url}}"></a>
Fig. Use of helpers
So, basically in the above code, we have used the helper “url-encode” and have passed the parameter “event.url” to it which we are getting from the model. Now we need to get this parameter in the url-encode.js file where we will encode it and return.
Accessing the params in helper:
import Ember from 'ember';
const { Helper } = Ember;
/**
* Helper to URL encode a string
* @param params
* @returns {*}
*/
export function urlEncode(params) {
if (!params || params.length === 0) {
return '';
}
return encodeURIComponent(params[0]);
}
export default Helper.helper(urlEncode);
The above code shows how we can access the params in the url-encode.js. ‘params’ is an array passed which can be accessed in the function directly. Now we just need to perform the action on the params and return it to the template. Here we are using ‘encodeURIComponent’ method to encode the URL and then returning it.
This is how the helpers work. They are a better way to reduce redundancy and help code structure better.
Resources:
Blog on DockYard about Helpers by Lauren Tan
Source code:
https://github.com/fossasia/open-event-frontend/blob/development/app/helpers/url-encode.js
Img src: 
I will be explaining step by step to achieve this using some code snippets.
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