Extending the Prototype

From now on, we'll pretty much be adding everything to the prototype key. But, it does get a little bit annoying to always need to say Helper.prototype.something = for every method:

76 lines web/assets/js/RepLogApp.js
... lines 1 - 2
(function(window, $) {
... lines 4 - 65
Helper.prototype.calculateTotalWeight = function() {
... lines 67 - 72
};
})(window, jQuery);

No worries! We can shorten this with a shortcut that's similar to PHP's array_merge() function. Use $.extend() and pass it Helper.prototype and then a second object containing all of the properties you want to merge into that object. In other words, move our calculateTotalWeight() function into this and update it to be calculateTotalWeight: function:

73 lines web/assets/js/RepLogApp.js
... lines 1 - 2
(function(window, $) {
... lines 4 - 60
$.extend(Helper.prototype, {
calculateTotalWeight: function() {
var totalWeight = 0;
this.$wrapper.find('tbody tr').each(function () {
totalWeight += $(this).data('weight');
});
return totalWeight;
}
});
})(window, jQuery);

At the bottom, we don't need the semicolon anymore. If we had more properties, we'd add them right below calculateTotalWeight: no need to worry about writing prototype every time.

There's nothing special about $.extend, it's just a handy array_merge-esque function that we happen to have handy. You may see other functions from other libraries that do the same thing.

Making RepLogApp an Instantiatable Object

With this trick, it's super easy to make RepLogApp an instantiatable object. First, set RepLogApp itself to the former initialize() function. I'll un-indent everything and finish it with a semicolon:

74 lines web/assets/js/RepLogApp.js
... lines 1 - 2
(function(window, $) {
window.RepLogApp = function ($wrapper) {
this.$wrapper = $wrapper;
this.helper = new Helper(this.$wrapper);
this.$wrapper.find('.js-delete-rep-log').on(
'click',
this.handleRepLogDelete.bind(this)
);
this.$wrapper.find('tbody tr').on(
'click',
this.handleRowClick.bind(this)
);
};
... lines 17 - 72
})(window, jQuery);

Constructor done!

Next, add $.extend() with window.RepLogApp.prototype and {. The existing keys fit right into this perfectly! Winning! At the end, add an extra ):

74 lines web/assets/js/RepLogApp.js
... lines 1 - 2
(function(window, $) {
... lines 4 - 17
$.extend(window.RepLogApp.prototype, {
updateTotalWeightLifted: function () {
this.$wrapper.find('.js-total-weight').html(
this.helper.calculateTotalWeight()
);
},
handleRepLogDelete: function (e) {
e.preventDefault();
var $link = $(e.currentTarget);
$link.addClass('text-danger');
$link.find('.fa')
.removeClass('fa-trash')
.addClass('fa-spinner')
.addClass('fa-spin');
var deleteUrl = $link.data('url');
var $row = $link.closest('tr');
var self = this;
$.ajax({
url: deleteUrl,
method: 'DELETE',
success: function () {
$row.fadeOut('normal', function () {
$(this).remove();
self.updateTotalWeightLifted();
});
}
});
},
handleRowClick: function () {
console.log('row clicked!');
}
});
... lines 55 - 72
})(window, jQuery);

Yes! In our template, we won't use RepLogApp like this anymore. Instead, say var repLogApp = new RepLogApp($table):

77 lines app/Resources/views/lift/index.html.twig
... lines 1 - 64
{% block javascripts %}
... lines 66 - 69
<script>
$(document).ready(function() {
var $table = $('.js-rep-log-table');
var repLogApp = new RepLogApp($table);
});
</script>
{% endblock %}

We won't call any methods on that new repLogApp variable, but we could if we wanted to. We could also create multiple RepLogApp objects if we had multiple tables on the page, or if we loaded a table via AJAX. Our JavaScript is starting to be awesome!

Leave a comment!

  • 2017-08-02 Victor Bocharsky

    Hey Jian,

    Yes, jQuery has extend() method, see the docs: https://api.jquery.com/jque... . So $.extend() calls this jQuery method if $ is an object of jQuery of course. JavaScript also has similar method, but it's called extends() (note the "s" at the end) - here's the docs: https://developer.mozilla.o... . But this JS methods is a part of ECMAScript 2015 only.

    Cheers!

  • 2017-08-01 jian su

    For the $.extend is this jquery method? In JavaScript there is also _.extend also do the same thing?