Javascript – backbone.js collection get vars

backbone.jscollectionsjavascript

This seems like an obvious one, but I'm somehow missing it…

How do you send options along with a backbone.js collection fetch()?

Or, from a broader point of view: I have a large dataset on the server, messages in this case, that I want to make accessible through a collection. Seeing as there could be thousands of messages I don't want to simply fetch and store all of them at once, so my collection would have to at least understand limits and offsets. Not to mention querying filtered or sorted lists.

Is a backbone collection even the way to handle this?

Cheers

Best Answer

I've been messing with Backbone for a couple days now and I had to deal with this problem almost immediately and I looked at this solution, but I found it clunky. After reading some more backbone documentation I discovered you can actually override any of the jQuery.ajax options within the fetch() method. So for example

Posts = Backbone.Collections.extend({
  model: Post,
  url: '/posts'
});

Now when you want to call fetch just send it whatever parameters you wish. e.g.

var posts = new Posts();
posts.fetch({ data: { page: 3, pagesize: 10, sort: 'asc' } });

This will produce the following request:

http://yourdomain/posts?page=3&pagesize=10&sort=asc

Anyway, I know you've already accepted an answer, but hopefully this will help someone.

Short & Snazzy:

+ new Date()

A unary operator like plus triggers the valueOf method in the Date object and it returns the timestamp (without any alteration).

Details:

On almost all current browsers you can use Date.now() to get the UTC timestamp in milliseconds; a notable exception to this is IE8 and earlier (see compatibility table).

You can easily make a shim for this, though:

if (!Date.now) {
    Date.now = function() { return new Date().getTime(); }
}

To get the timestamp in seconds, you can use:

Math.floor(Date.now() / 1000)

Or alternatively you could use:

Date.now() / 1000 | 0

Which should be slightly faster, but also less readable.
(also see this answer or this with further explaination to bitwise operators).

I would recommend using Date.now() (with compatibility shim). It's slightly better because it's shorter & doesn't create a new Date object. However, if you don't want a shim & maximum compatibility, you could use the "old" method to get the timestamp in milliseconds:

new Date().getTime()

Which you can then convert to seconds like this:

Math.round(new Date().getTime()/1000)

And you can also use the valueOf method which we showed above:

new Date().valueOf()

Timestamp in Milliseconds

var timeStampInMs = window.performance && window.performance.now && window.performance.timing && window.performance.timing.navigationStart ? window.performance.now() + window.performance.timing.navigationStart : Date.now();

console.log(timeStampInMs, Date.now());

Java – Iterating through a Collection, avoiding ConcurrentModificationException when removing objects in a loop

Iterator.remove() is safe, you can use it like this:

List<String> list = new ArrayList<>();

// This is a clever way to create the iterator and call iterator.hasNext() like
// you would do in a while-loop. It would be the same as doing:
//     Iterator<String> iterator = list.iterator();
//     while (iterator.hasNext()) {
for (Iterator<String> iterator = list.iterator(); iterator.hasNext();) {
    String string = iterator.next();
    if (string.isEmpty()) {
        // Remove the current element from the iterator and the list.
        iterator.remove();
    }
}

Note that Iterator.remove() is the only safe way to modify a collection during iteration; the behavior is unspecified if the underlying collection is modified in any other way while the iteration is in progress.

Source: docs.oracle > The Collection Interface

And similarly, if you have a ListIterator and want to add items, you can use ListIterator#add, for the same reason you can use Iterator#remove — it's designed to allow it.

In your case you tried to remove from a list, but the same restriction applies if trying to put into a Map while iterating its content.

Best Answer

Related Solutions

Javascript – How to get a timestamp in JavaScript

Short & Snazzy:

Java – Iterating through a Collection, avoiding ConcurrentModificationException when removing objects in a loop

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