Question

tutorial: http://www.jamesyu.org/2011/01/27/cloudedit-a-backbone-js-tutorial-by-example/
I am going through the CloudEdit rails/backbone.js tutrorial and got stuck on the very first chunk of code. here it is:

var Document = Backbone.Model.extend({
  url : function() {
    var base = 'documents';
    if (this.isNew()) return base;
    return base + (base.charAt(base.length - 1) == '/' ? '' : '/') + this.id;
  }
});

the line I am struggling with is this

return base + (base.charAt(base.length - 1) == '/' ? '' : '/') + this.id;

Since base = 'documents' isn’t base.charAt(base.length - 1) = s ?
I know what it is supposed to do, I am just wondering why it does it. Does the value of base change to documents/ sometimes? Why not just write return base+'/'+this.id

Answer 1

That line is the equivalent of

if last character is '/'
   return base + this.id
else 
   return base + '/' + this.id

just having return base+'/'+this.id would result in a url of “documents//6” for a model with base="documents/" and id=6

Update
As Adam Lassek mentioned in the comments, that line of should simply be written as

return base+'/'+this.id

for this example as the base variable is defined in that same block. However that line of code is also in the backbone.js source code and its purpose is as described above.

Instead of overriding the url method you should set the urlRoot attribute in the model:

var Document = Backbone.Model.extend({
  urlRoot : 'documents'
});