RxJS proper way to merge 3 arrays into one, as an Observable -


hi have 3 subjects ( observables )

 const arr1$ = new behaviorsubject([])  const arr2$ = new behaviorsubject([])  const arr3$ = new behaviorsubject([])

let's these subjects contain data

arr1 = ['1','2'],  arr2 = ['3','7'],  arr3 = ['4']

i want create observable (mergedobservable) combines latest these 3 observables, merges them 1 array, result 1 array this: ['1','2','3','7','4']

so can achieve  this.mergedobservable.subscribe( mergedarray => {      console.log(mergedarray) }) // ['1','2','3','7','4']

i struggling how make 'mergedobservable'. have tried combinelatest(arr1$,arr2$,arr3$) , still need 'chain' more functionality merge 3.

thanks!

combinelatest takes optional project function can used modify combined value.

you can specify project function uses array.prototype.reduce flatten arrays single array:

const arr1$ = new rx.behaviorsubject(['1','2']);  const arr2$ = new rx.behaviorsubject(['3','7']);  const arr3$ = new rx.behaviorsubject(['4']);    rx.observable    .combinelatest(      arr1$, arr2$, arr3$,      (...arrays) => arrays.reduce((acc, array) => [...acc, ...array], [])    )    .subscribe(value => console.log(value));
.as-console-wrapper { max-height: 100% !important; top: 0; }
<script src="https://unpkg.com/rxjs/bundles/rx.min.js"></script>


Comments

Post a Comment

Popular posts from this blog

Is there a better way to structure post methods in Class Based Views -

i'm using class based views in django , never specify url in ajax calls , omit action parameter in form because know these requests go through post method of class based view. notice view - profile page make many requests depending on user updating on page - post method become convoluted , if/else mess example: def post(self, request, *args, **kwargs): # handle user changing available date if request.post.get('availabledate') != none: self.updateavailabledate(request) return jsonresponse({'result':'success'}) if request.post.get('newprojectname') != none: creative_user = creativeuserprofile.objects.get(id = request.user.id) project = project.create_project(creative_user, request.post['newprojectname']) project.save() return jsonresponse({'projectid': project.id }) if request.post.get('projectimage') != none , request.files['file']: proj
Read more

performance - Why is XCHG reg, reg a 3 micro-op instruction on modern Intel architectures? -

i'm doing micro-optimization on performance critical part of code , came across sequence of instructions (in at&t syntax): add %rax, %rbx mov %rdx, %rax mov %rbx, %rdx i thought had use case xchg allow me shave instruction , write: add %rbx, %rax xchg %rax, %rdx however, dimay found agner fog's instruction tables , xchg 3 micro-op instruction 2 cycle latency on sandy bridge, ivy bridge, broadwell, haswell , skylake. 3 whole micro-ops , 2 cycles of latency! 3 micro-ops throws off 4-1-1-1 cadence , 2 cycle latency makes worse original in best case since last 2 instructions in original might execute in parallel. now... cpu might breaking instruction micro-ops equivalent to: mov %rax, %tmp mov %rdx, %rax mov %tmp, %rdx where tmp anonymous internal register , suppose last 2 micro-ops run in parallel latency 2 cycles. given register renaming occurs on these micro-architectures, though, doesn't make sense me done way. why wouldn't register renamer
Read more

jquery - Responsive Navbar with Sub Navbar -

good day, forgive me nav vocabulary not best. if question confusing apologize. i'm working on navigation bar needs centered on page @ 768px , above. items in nav open (or perhaps toggle) subnav lives directly below. these nav should appear centered on page. i have been able work through responsive portion of nav bar, having main items align vertically , sub nav menu of each item roll out below, , gave them indent separation. working well. however, issue not responsive side, behavior @ width greater 768px. happens toggling menu's sub navigation pushes other main items down page below sub nav. here's code: $(document).ready(function () { //stick in fixed 100% height behind navbar don't wrap $('#slide-nav.navbar-inverse').after($('<div class="inverse" id="navbar-height-col"></div>')); $('#slide-nav.navbar-default').after($('<div id="navbar-height-col"></d
Read more