Data not being fetched from json file - json

Question

I am trying to fetch data from the static json file but the data is not getting displayed at all. What could be the possible reason for it.
Below is my code:
var Collection = Backbone.Collection.extend({
url: "names_of_people.json",
initialize: function() {
this.fetch();
}
});
collections = new Collection();
console.log("the length "+collections.length);
for (i=1;i<collections.length;i++)
{
console.log("done "+ collections.at(i).get("name"));
}

Answer 1

The problem is that this code:
console.log("the length "+collections.length);
for (i=1;i<collections.length;i++)
{
console.log("done "+ collections.at(i).get("name"));
}
ends up being executed before this.fetch() has completed. You'll need to either put your code in this.fetch's success callback, like this:
var Collection = Backbone.Collection.extend({
url: '/data.json',
initialize: function() {
this.fetch({
success: function() {
console.log(collections, 'the length ' + collections.length);
for (var i = 0; i < collections.length; i++) {
console.log('done ' + collections.at(i).get('name'));
}
}
});
}
});
var collections = new Collection();
or by listening to the collection's sync event, which occurs when this.fetch has completed successfully. This pattern is more commonly used in Backbone applications.
var Collection = Backbone.Collection.extend({
url: '/data.json',
initialize: function() {
this.listenTo(this, 'sync', this.syncExample);
this.fetch();
},
syncExample: function() {
console.log(collections, 'the length ' + collections.length);
for (var i = 0; i < collections.length; i++) {
console.log('done ' + collections.at(i).get('name'));
}
}
});
var collections = new Collection();
You can read more about Backbone's event system and the listenTo function here.

Answer 2

check backbone parse function. after fetch it will also call vlidate and parse if they exist.
EDIT: more detail
The key thing here I think is, the fetch() is asynchronous, so by the time you start loop, the data is not here yet. So you need to execute the code when you are sure the collection is ready. I usually listen to a "reset" event, and let the fetch to fire a reset event by collection.fetch({reset:true}).
Backbone Collection, whenever fetch, and get an array of data from server in a format
[obj1,obj2],
it will pass each of these into a parse function, described here
For debug purpose you can simply do:
var MyCollection=Backbone.Collection.extend({
parse:function(response){
console.log(response);
return response;
}
})
This can check if the fetch indeed get the json.
On a side note, it is always a good practise to fetch it after you initialized the collection, means you don't put the this.fetch() inside initialize(), you do this outside.
for example, if you want to print out all the element name, you can do
var c=MyCollection();
c.fetch({reset:true}); // this will fire 'reset' event after fetch
c.on('reset',printstuff());
function printstuff(){
_.forEach(c,function(e){
console.log(e.get('name'));
});
}
Note this 'reset' event fires after all the collection is set, means it is after the parse() function. Apart from this parse(), there is also a validate function that is called by model. You collection must have a model parameter, you can make your own model, and give it a validate(), it also print out stuff.