Transitioning between models on a ng-repeat - javascript

I'm building a directive (Angular 1.2) that will toggle between displaying two different lists - think of them as a list of "trending" items on the site and a list of items the user is "following". So we have a toggle that allows the user to choose which list is being displayed, with an ng-repeat below it showing the items.
There will be a good deal of overlap between these lists, and when the user toggles from one list to the other, I'd like items that are contained in both to transition from their places on the "outgoing" list to their places on the new one, rather than disappearing and reappearing.
My question isn't about how to achieve the actual animations (we're using ngAnimate), but about how I should structure the controller/data to. I'm thinking about my directive controller having a trendingList and a followingList (that contain the actual data items), and an activeList that points to whichever of the two are currently being displayed. So the ng-repeat is actually on activeList, and toggling is essentially:
$scope.toggleMode = function(){
if ($scope.mode == 'trending')
$scope.mode = following;
$scope.activeList = followingList;
else {/*the inverse...*/}
}
Is that the most reasonable approach? If so, how do I ensure that angular recognizes the equality of objects present in both lists?
Or is there an easier/cleaner way to do this?

From what I understand, angular isn't tracking the equality of objects in the list it is repeating. The animations are triggered when the DOM is manipulated, not when the data changes (though data changes will change the DOM). As to what you should do, I don't have experience with this problem so hopefully somebody can point you in the right direction!

Related

Table in AngularJS app with many "select" elements built with ng-repeat takes very long

I have a table with variable number of records (could be up to hundreds) where its body is build with one ng-repeat.
Within each record, there are two input fields of type select where their contents is also built using ng-repear and the number of options for each is about 100.
This is working right now, except that it takes a lot of time for the page to be built (several seconds; I guess due to the large number of html records that AngularJS is adding to the DOM).
Here is an example of one of the selects:
<select class="form-control" ng-model="One_Source.Measuring_Method_Code">
<option ng-selected="{{One_Method.Value == One_Source.Measuring_Method_Code}}"
ng-repeat="One_Method in All_Collections.Parameters_Test_Methods"
value="{{One_Method.Value}}"
title="{{One_Method.Test_Method_Name}} | {{One_Method.Method_Internal_Name}}">
{{One_Method.Value}}
</option>
</select>
Two questions:
Is there a simple way to speed up the page building process?
As shown in the example, each option in the list has a title clause displaying a detailed description of the option's meaning. How can I add a title to the select showing the description of the current value?
For the first question I was thinking about building the list of options for each select element only upon clicking on it, but I'm not sure if that would be the best way to do it.
Try using one time bindings so that Angular doesn't watch the value by prefixing it with ::. It can also be more efficient to use track by in your ng-repeat if each row has a unique value, like an ID.
<option
ng-selected="{{One_Method.Value == One_Source.Measuring_Method_Code}}"
ng-repeat="One_Method in All_Collections.Parameters_Test_Methods track by One_Method.id"
value="{{::One_Method.Value}}"
title="{{::One_Method.Test_Method_Name}} | {{::One_Method.Method_Internal_Name}}"
>
{{::One_Method.Value}}
</option>
If you still can't gain the performance you're expecting from #doublesharps's answer, you will have to implement one of the following:
You could build a custom list that has a 'load more' button which would destroy say the first '50' options and load the next 50.
A better option would be to turn this into an autocomplete, where the user searches for values.
Virtual repeat - Something angular material does really well, it constantly draw's and re-draws new elements based on the scroll position inside the element.
Other resources:
http://blog.scalyr.com/2013/10/angularjs-1200ms-to-35ms/
https://github.com/stackfull/angular-virtual-scroll
http://klajd.github.io/angular-virtual-repeat/#/Home
I found a PARTIAL SOLUTION that still needs to be polished but is quite promising.
During creation of the page, I do not make use of ng-repeat for the options but instead deploy a single option with the value received for the field from the database (if any, otherwise the select element is left blank).
When the user clicks on the select element a $scope function is invoked that checks the number of options within the select element and, if less or equal to 1, the inner HTML of this select element is re-generated and deployed.
Though clicking on all these select in the page will take (accumulative) a comparable time as when built upon load, this time is distributed over several events (the user clicking on all the select elements) and hence it is not perceived by the user.
Now, by polishing I mean that there is a strange behavior. In order to see the generated list of options, I need to click on the select twice. Will keep investigating this and post the solution (hoping I find one).

Aurelia JS - multi level binding/update?

I'm not sure whether I'm using the right terminology here - but here is an example:
https://gist.run/?id=57ed46429e4583eb4c3fb11814451a55
This is how it looks like in Chromium:
Basically, the entries on top (red outline) are a visualization of an array as the "first-level" data display; here one can toggle each element's selection, and make a multi-element selection (red background). The array that is the source of the "first-level" display is mydata in first-level-items.js.
Those items that are selected in "first-level", are then shown again in "second-level" (green outline); here the same information of name and value is displayed, although a bit differently. Here also one can toggle an elements selection - but only one "second-level" element can be selected. The array that is the source of the "second-level" display is myseldata in second-level-items.js.
The intent here, is that once a "second-level" selection has been made, a slider appears, to change the .value property of the particular object which is the selected array element.
My original question (which is why I started this post/example at all), was:
How do I ensure that whenever the slider is changed, the value is updated in both second-level and first-level display?
... however, for reasons beyond me, this in fact does work somewhat in this gist.run example (but it still doesn't work in my actual project, which forced me to come up with the example to begin with). Also it only works somewhat, in the sense that when loading the example page at first, after making first and second level selections, and then changing the slider, the .value will be updated in both first- and second-level display. But as soon as I try deselecting on second level - or changing the selection on second level - then updating stops. So, I guess this question still stands...
After a second-level selection has been made, deselecting on second level (by clicking to toggle) does NOT remove the slider; how can I have it behave like that?
The update happens only on the slider's onChange - basically, while you drag and slide, this component emits onSlide, but it will generate onChange only at the end when the mouse is released (that is, when the sliding has stopped). How can I update both first- and second- level display while the slider is sliding?
And finally - is this how this kind of a problem is best addressed in Aurelia? That is - I currently have one array in first-level-items.js; first-level-items.js then has a singleton reference to second-level-items.js, so it can call a method within it, to change a filtered copy of the array on the second level, which then serves as a source both for second-level display and the slider... Is there a better way to organise this?
Boy, this was a pain, but here's what I think is the solution:
https://gist.run/?id=c09fea3b82a9ebc41e0a4c90e8665b04
Here are some notes:
Apparently, there is something wrong applying if.bind or show.bind on the input element of the slider - instead, the input element should be put in an enclosing div, and the div should have if/show.bind applied
Furthermore, if.bind should not be used, as it re-instantiates the slider element - use show.bind so we can get a reference to the slider widget at start already, even if it is hidden
Seemingly, using TaskQueue in attached() is the only way to get a reference to the slider at start
Once we have a reference to the widget, re-apply it on each second level element, whenever they change
Do not set this.myselChanging to null to specify no target of the slider (simply count on hiding the slider appropriately)
For a continuous change (onSlide), simply use this.myselChanging.value = e.value; in the handler - both first-level and second-level values will be changed
Beyond this, it seems arrays are copied by reference, so the multi-level update happens without further intervention...
Though, would still love to know what is the proper way to do this...

Animate React rearranging of list items

I have an array of JSON objects that are used to render a list of elements:
mydata.map(thing => {
return <SomeComponent key={thing._id} />
});
Each rendered item has up/down arrows, and if the user clicks the up arrow, for example, the item will be moved up the list. On the back end, the items in the array are simply swapped.
How can I make this process animate so it's easier for the user to see what the result of their action was? I was looking into react-motion, but it seems to work based on modifying CSS/styles. I was hoping there would be something that uses React's key property to determine unique elements and handle movement based on that.
Any suggestions?
React-flip-move is a wonderful component which allows you to animate children components. There is an example animation flipping values on a list too.

AngularJS fixed list with updating content

Im in need of some inspiration on how to solve the following:
I'm making an information monitor using AngularJS.
The monitor should list a maximum of 6 rows of information.
A new row will always be put on top of the others and pushed in from the top. If there are already 6 rows, the last row will be pushed out from the bottom.
A row may disappear from the list at any given time.
Visually, I would very much like it to be sort of scrolling, so when a new row is to be displayed, it will slide in from the top, and all the items will slide a row down.
I'm not sure how to implement the above. I've thought about ng-repeat, but I don't know how to move the items when an element appears or is deleted.
I hope somebody can give me some advice.
For add new item in top list, use a unshift method of javascript. For example:
var list = [0,1,2]
list.unshift(3)
// results [3,0,1,2]
remember, add and remove items in $scope of list for update her.
$scope.list = [1,2,3,4,5,6];
$scope.list.unshift(9); // [9,1,2,3,4,5,6];
$scope.list.pop(1); // [9,2,3,4,5,6];
In HTML, continue using ng-repeat normally
You're going to want to look at ngAnimate. It has built-in support for working with ng-repeat including animations on the addition and deletion of items from a list.
https://docs.angularjs.org/api/ngAnimate
The docs for the integrations with ngRepeat are here: https://docs.angularjs.org/api/ng/directive/ngRepeat#animations

Highlight last inserted document in Meteor

I have form and list of objects at the same page. When I insert a new row, it is not very easy to see where the newly inserted row is placed. Therefore, I thought I could color/highlight the newly inserted row (and perhaps remove the highlight after a few seconds).
How can I do this? I think a way to do this could be using a method on the server which returns the inserted id (return Collection.insert(doc);) and on the client use a callback with
Meteor.call('insertDoc', function(err,result) {
// do something with result
});
I think I can use a reactive-var to save the id of the last inserted row and in the loop highlight the row with
{{#each docs}}
<li class="{{isActive}}">{{name}}</li>
{{/each}}
and have a helper to return active if this._id equals the reactive var with the last inserted id.
But is this the best way to do it? How can I remove the color after some seconds? I have seen such behaviour on many pages but I cannot find any tutorials/code snippets to achieve this.
I wrote a package that uses Meteor's UI hooks to fade items in and out of a list as they are added and removed, to help users maintain context as data changes:
https://github.com/mizzao/meteor-animated-each
There is a demo at http://animated-each.meteor.com/. You can see that as items are added and removed, they are faded in and out. If items are inserted off the screen, the visible area does not scroll.
This isn't doing exactly what you want, but you can use the same idea to highlight items as they appear as well, as opposed to the simple fade in.
Note that all of this happens at the UI rendering level - not the template/code level. The UI hooks are also not well documented right now, but they've been around for a while.
I don't know if your method is the best, but that's how I'd go about doing it.
As for the animation, I'd use a CSS3 animation. Plenty to choose from ( https://developer.mozilla.org/en-US/docs/Web/CSS/animation ), and you can easily make them fade to the standard color. The animation would also only be applied to the last inserted item (because of the way you did it, only the last item would have the "active" class)

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