I fetch the data from a server and some items have a specific attribute others don't. I need to sort data according to this specific attribute and I am using sortBy package but of course it doesn't work properly because when it tries to sort data and doesn't find the attribute, it is broken.
myItems.sort(sortBy('specificAttr'))
Basically, what I did (think of inside of a loop):
if(!myItems.specificAttr) {myItems.speficificAttr = 0);
I know it doesn't make sense at all, but I don't know what I can do.
Do you have any advice with code examples?
Using lodash's sortBy
Lodash handles this case out of the box. If it can't find the attribute, it gets pushed to the end of the sorted array.
var users = [
{ 'age': 48 },
{ 'user': 'barney', 'age': 36 },
{ 'user': 'fred', 'age': 40 },
{ 'user': 'barney', 'age': 34 }
];
_.sortBy(users, [(o) => { return o.user; }]);
// => objects for barney, barney, fred, and no-name in that order
_.sortBy(users, ['user']);
// => objects for barney, barney, fred, and no-name in that order
If you're using some other library's sortBy, check the documentation to see if there's an optional second argument that would allow you to customize the attribute getter function.
Rolling your own
If you're implementing your own sorting algorithm, simply do a check like if myItem.specificAttr to check if the attribute exists while you're doing the actual sorting (rather than prior sorting, as you described in your example).
Related
I generally have problems using rxjs with nested Objects or Arrays.
My current use-case is this:
{a: [
{b: 0, c:[{d:1}]},
{b: 1, e:[{f: 'someString'}]}
]
Task: Get and set the Observable or value of a,b,c,d,e,f. I also want to be able to subscribe to each property.
I had this Problem in a similar use-case with an Array of BehaviorSubjects:
Efficiently get Observable of an array BehaviorSubjects
I generally have problems to use the basic functionality of nested arrays/objects in rxjs.
The basic functionality I mean includes:
Array:
getting Element by Index
using for of/in on Arrays
setting an Element by Index
push, pop, shift, slice, splice, ...
Object:
getting Value by Property name
going into the nested tree: object.key1.key2.key3[3].key4 ...
setting Value by Property name
assign
for of/in loops
Generally:
Destructuring: e.g.: let [variable1, variable2] = someObject;
Maybe other stuff I forgot.
I dont know if and which functions are possible for which rxjs Objects and which make sense (for example you should be able to set values in an Observable directly). But coming from a background without rxjs, I have trouble to manage my rxjs Objects properly.
I think reason for this besides my lack of knowledge and understanding is, that
a. The rxjs Objects don't provide the functionality as I'm used to from normal arrays and objects. e.g.:
let variable1 = array[1].property;
//becomes this (see related stack-Question I mentioned earlier)
let variable2 = array.pipe(mergeMap(d=> d[index].pipe(map(d1 => d1[property]));
// -> what happens here? You first need to know what mergeMap,
// map is doing and you have 5 levels of nested inline functions.
b. To implement the those mentioned functionalities I need to go over the .pipe() function and use some function like mergeMap, map, pluck, ... Functions that aren't directly indicating that you can get the Observable of let's say 'e' in my example. Making something like object.a[1].e wierd to implement (at least I don't know how to do that yet)
EDIT:
I also want to note, that I still love the idea of rxjs which works well in angular. I just have problems using it to it's full extend, as I'm a bit new to angular and consequently rxjs.
I thin RX is mainly focus on dealing with async operations. Mutation of array and object we can perfectly use the methods comes natively with javascript if theres no existing operators. or you can create your own operator for mutation/iteration etc.
Will try to answer some of your question on array/objects mutation, they are actually very straight forward.
Array:
getting Element by Index
map(arr=>arr[index])
using for of/in on Arrays
map(arr=>arry.map(item=>....))
setting an Element by Index
tap(arr=>arr[index]=somevalue)
Object:
getting Value by Property name
pluck('name')
going into the nested tree: object.key1.key2.key3[3].key4 ...
pluck('key1','key2')
setting Value by Property name
map(obj=>({a:value,obj...}))
assign
lets say your really want some pick array index method as rxjs operator you can create something like, same as for..in operations.
const pluckIndex=(index)=>source=>source.pipe(map(arr=>arr[index]))
const source = of([2,3])
source.pipe(pluckIndex(1)).subscribe(x => console.log(x));
I have an array with a few items in it. Every x seconds, I receive a new array with the latest data. I check if the data has changed, and if it has, I replace the old one with the new one:
if (currentList != responseFromHttpCall) {
currentList = responseFromHttpCall;
}
This messes up the classes provided by ng-animate, as it acts like I replaced all of the items -- well, I do actually, but I don't know how to not.
These changes can occur in the list:
There's one (or more) new item(s) in the list - not necessaryly at the end of the list though.
One (or more) items in the list might be gone (deleted).
One (or more) items might be changed.
Two (or more) items might have been swapped.
Can anyone help me in getting ng-animate to understand what classes to show? I made a small "illustation" of my problem, found here: http://plnkr.co/edit/TS401ra58dgJS18ydsG1?p=preview
Thanks a lot!
To achieve what you want, you will need to modify existing list on controller (vm.list) on every action. I have one solution that may work for your particular example.
you would need to compare 2 lists (loop through first) similar to:
vm.list.forEach((val, index)=>{
// some code to check against array that's coming from ajax call
});
in case of adding you would need to loop against other list (in your case newList):
newList.forEach((val, index)=>{
// some code to check array on controller
});
I'm not saying this is the best solution but it works and will work in your case. Keep in mind - to properly test you will need to click reset after each action since you are looking at same global original list which will persist same data throughout the app cycle since we don't change it - if you want to change it just add before end of each function:
original = angular.copy(vm.list);
You could also make this more generic and put everything on one function, but for example, here's plnkr:
http://plnkr.co/edit/sr5CHji6DbiiknlgFdNm?p=preview
Hope it helps.
I would like to know if there is any simple way in logstash to copy all the elements of one field array to another. Put another way, is there a way to copy all the nested fields of a top-level field to another top-level field?
I'm having this problem because I'm dealing with a nonstandard multiline log format which is not necessarily thread-safe. So in order to make sure I get all the data I need and in the right order, I'm currently on planning on throwing every relevant value of each type into an array, and then sorting them out later. The problem I'm having is that logstash doesn't seem to support too much array manipulation. If you think my approach just won't work at all in logstash, any suggestions as to what I could do instead would be greatly appreciated.
Thanks!
As this question almost shows: LogStash: How to make a copy of the #timestamp field while maintaining the same time format? you can use the ruby filter to copy an array.
filter {
ruby {
code => "event['another_top_level_field'] = event['top_level_field']"
}
}
I use to use the where method from the Collections in backbone. But I don't see how to fetch this result:
MyCollection.Group[x].id
As you can guess, MyCollection is the collection, Group is an array, and id is the field I would like to match for a specific value, something like:
MyCollection.findWhere(Group[x].id: 34);
I have seen the "contains" function of underscore but it doesn't seems to work with associative arrays
Is there a way to do it or should we parse the collection manually using Javascript ?
Collection.where and Collection.findWhere are convenience functions for simple filters. In your case, you would use the more complex Collection.find (proxied to _.find)
find _.find(list, iterator, [context])
Looks through each value in the list, returning the first one that passes a truth test
(iterator). The function returns as soon as it finds an acceptable
element, and doesn't traverse the entire list.
And if I understand correctly your condition, it could look like
MyCollection.find(function(model) {
return _.findWhere(model.get('Group'), {id: 34});
})
you can choose to use jQuery .find() . see examples here: http://api.jquery.com/find/
I have backbone collection of models and would like to retrieve the distinct values of a certain property
If I have loaded data like the following into my collection:
[{brand:'audi',id:'1234'},
{brand:'audi',id:'3456'},
{brand:'bmw',id:'3456'}]
I would now want to get the distinct brands from the collection. The result should be:
['audi','bmw']
Looking at the Backbone and Underscore API I don't see anything obvious to achieve this.
My current approach would be to use a library like jslinq
Am I missing anything obvious or does somebody have a better suggestion than jslinq?
You can use pluck and then use uniq (example: http://jsfiddle.net/sCVyN/5/)
pluck
A convenient version of what is perhaps the most common use-case for
map: extracting a list of property values.
uniq
Produces a duplicate-free version of the array, using === to test
object equality. If you know in advance that the array is sorted,
passing true for isSorted will run a much faster algorithm. If you
want to compute unique items based on a transformation, pass an
iterator function.