Can one avoid multiple DOM elements with same id, when using Backbone/Marionette view instances? - marionette

Question

When I create multiple view instances of the Marionette view which is linked with a template html with ids, these would get duplicated for multiple instances of these views.
While it works correctly, I feel that there ought to be more architecturally correct way of doing this.
The example code is like below.
Template:
<script id="myTemplate" type="text/template">
<div id="myDiv">
<input type="text" id="myText"/>
<input type="button" id="myBtn" value="Click me!"/>
</div>
</script>
View:
MyView = Backbone.Marionette.ItemView.extend({
template: '#myTemplate',
events: {
'click #myBtn' : 'myFunc' //Correctly identifies its own 'myBtn'
},
myFunc : function() {
alert($('myText').val()); //Again, picks own 'myText'
}
});
var v1= new MyView();
v1.render();
var v2= new MyView();
v2.render(); //Duplicate IDs now present in DOM
I need some unique identification of these DOM elements and hence the ids.
Even when tying the model to this view, we need some way to identify these DOM elements.
What is the correct way of doing this without duplicating the ids.

Answer 1

Just pass the id to the view when you create it:
Template:
<script id="myTemplate" type="text/template">
<input type="text" class="js-myText"/>
<input type="button" class="js-myBtn" value="Click me!"/>
</script>
View def:
MyView = Backbone.Marionette.ItemView.extend({
template: '#myTemplate',
events: {
'click #myBtn' : 'myFunc' //Correctly identifies its own 'myBtn'
},
myFunc : function() {
alert($('myText').val()); //Again, picks own 'myText'
}
});
Instanciation:
var v1= new MyView({ id: "view" + number});
v1.render();
Then you can provide dynamic id values for your views (e.g. by using a model id).
That said, when using Marionette you shouldn't need to call render: you should instead show a view within a region. Take a look at the free sample to my Marionette book to get you up to speed.

Answer 2

If you must go for unique IDs to make sure no one accidentally duplicates a class name inside a view, you can use:
Underscore's uniqueId method to generate a unique ID for each DOM element inside the view, like: <input type="text" id= <%= _.uniqueId("myText_") %> /> This will just make sure that IDs are not duplicated. But they're not very helpful if you need to identify the elements by these IDs.
Marionette's TemplateHelpers which allow you to use helper functions from inside the templates:
//Define this inside your view:
templateHelpers: function() {
var that = this;
return {
getIdSuffix : function() { return that.idSuffix; }
/*Where idSuffix is passed to the view during instantiation
and assigned to this.idSuffix */
};
}
//In the template:
<input type="text" id= <%= "myText_" + getIdSuffix() %> />
You now know before runtime what DOM IDs you will have, provided care is taken not to give the same idSuffix to more than one view instance.

Answer 3

Simply put, don't use an id if it's not unique. Use a class or some other way of identifying the element.
You can use any jQuery selector to locate the element you want, ranging from the insane and brittle:
this.$('div > input:first'); // don't actually do this!
to the slower but semantically better:
this.$('[data-element-type="some-text-box-descriptive-name"]');
Although in reality, using a class is best, because that's what a class is for - for identifying a type of element. I can see that a maintainer might not know not to change your class in the template, so a data-attribute might be acceptable, or maybe even (in this case):
this.$('input[type=text]');