What is the obj?.prop syntax in javascript?












7















I was looking through a code and I came across this:



{{abc?.xvy=== tyu?abc?.xz:abc?.xz}}


I am unable to understand meaning of this expression.
Any help is much appreciated






javascript ecmascript-5







share|improve this question

























  • Possible duplicate of Null-safe property access (and conditional assignment) in ES6/2015

    – adiga
    28 mins ago
















7















I was looking through a code and I came across this:



{{abc?.xvy=== tyu?abc?.xz:abc?.xz}}


I am unable to understand meaning of this expression.
Any help is much appreciated






javascript ecmascript-5







share|improve this question

























  • Possible duplicate of Null-safe property access (and conditional assignment) in ES6/2015

    – adiga
    28 mins ago














7












7








7


0






I was looking through a code and I came across this:



{{abc?.xvy=== tyu?abc?.xz:abc?.xz}}


I am unable to understand meaning of this expression.
Any help is much appreciated






javascript ecmascript-5







share|improve this question
















I was looking through a code and I came across this:



{{abc?.xvy=== tyu?abc?.xz:abc?.xz}}


I am unable to understand meaning of this expression.
Any help is much appreciated






javascript ecmascript-5




javascript ecmascript-5






share|improve this question















share|improve this question













share|improve this question




share|improve this question








edited 21 mins ago









adiga

7,96962141




7,96962141










asked 38 mins ago









Apurva PathakApurva Pathak

1049




1049













  • Possible duplicate of Null-safe property access (and conditional assignment) in ES6/2015

    – adiga
    28 mins ago



















  • Possible duplicate of Null-safe property access (and conditional assignment) in ES6/2015

    – adiga
    28 mins ago

















Possible duplicate of Null-safe property access (and conditional assignment) in ES6/2015

– adiga
28 mins ago





Possible duplicate of Null-safe property access (and conditional assignment) in ES6/2015

– adiga
28 mins ago












4 Answers
4






active

oldest

votes


















3














This looks to be an example of the optional chaining proposal, which is still very much a work in progress (only at Stage 1). It's not actually implemented in vanilla JS environments yet. Using



obj?.prop


means: if obj is undefined or null, the expression evaluates to undefined. But otherwise, it will evaluate to the prop property on the object. This is syntax sugar for



obj && obj.prop


(using just obj.prop alone will throw if obj is undefined or null)



So, your



abc?.xvy=== tyu?abc?.xz:abc?.xz


will evaluate to true if the nested value abc?.xvy is equal to the nested value abc?.xz - or, it will evaluate to true if at least one of the nested values doesn't exist, and the other is undefined.



Spaced out for easier reading:



abc?.xvy === tyu

? abc?.xz

: abc?.xz


As you can see, both ? and : expressions are the same, making the conditional operator unnecessary here. An equivalent test (assuming that referencing tyu doesn't throw) would be



abc?.xvy === abc?.xz





share|improve this answer































    3














    Its new ES proposal called "optionals" for safe check reading for object properties. Above expression is equivalent to:



    (abc && abc.xvy) === (tyu) ? (abc && xz) : (abc && abc.xz)


    You can find more details here: https://github.com/davidyaha/ecmascript-optionals-proposal






    share|improve this answer

































      2














      It's called Null Propagation Operator.



      We can think of each ?. operator as a short circuit where "if the expression up until this point is null or undefined, then the whole expression evaluates to undefined".
      We could also optionally call functions.






      share|improve this answer































        -1














        It is called the elvis operator



        It is a part of the ECMAScript proposals to make code more readable and reduce the long && chains



        essentially, it creates a short-circuit check for null or undefined and prevents the "Cannot read property of undefined" errors. If the value exists, the latter part is evaluated.



        You can read more here : Is there a null-coalescing (Elvis) operator or safe navigation operator in javascript?






        share|improve this answer

























          Your Answer






          StackExchange.ifUsing("editor", function () {
          StackExchange.using("externalEditor", function () {
          StackExchange.using("snippets", function () {
          StackExchange.snippets.init();
          });
          });
          }, "code-snippets");

          StackExchange.ready(function() {
          var channelOptions = {
          tags: "".split(" "),
          id: "1"
          };
          initTagRenderer("".split(" "), "".split(" "), channelOptions);

          StackExchange.using("externalEditor", function() {
          // Have to fire editor after snippets, if snippets enabled
          if (StackExchange.settings.snippets.snippetsEnabled) {
          StackExchange.using("snippets", function() {
          createEditor();
          });
          }
          else {
          createEditor();
          }
          });

          function createEditor() {
          StackExchange.prepareEditor({
          heartbeatType: 'answer',
          autoActivateHeartbeat: false,
          convertImagesToLinks: true,
          noModals: true,
          showLowRepImageUploadWarning: true,
          reputationToPostImages: 10,
          bindNavPrevention: true,
          postfix: "",
          imageUploader: {
          brandingHtml: "Powered by u003ca class="icon-imgur-white" href="https://imgur.com/"u003eu003c/au003e",
          contentPolicyHtml: "User contributions licensed under u003ca href="https://creativecommons.org/licenses/by-sa/3.0/"u003ecc by-sa 3.0 with attribution requiredu003c/au003e u003ca href="https://stackoverflow.com/legal/content-policy"u003e(content policy)u003c/au003e",
          allowUrls: true
          },
          onDemand: true,
          discardSelector: ".discard-answer"
          ,immediatelyShowMarkdownHelp:true
          });


          }
          });














          draft saved

          draft discarded


















          StackExchange.ready(
          function () {
          StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fstackoverflow.com%2fquestions%2f54528778%2fwhat-is-the-obj-prop-syntax-in-javascript%23new-answer', 'question_page');
          }
          );

          Post as a guest















          Required, but never shown

























          4 Answers
          4






          active

          oldest

          votes








          4 Answers
          4






          active

          oldest

          votes









          active

          oldest

          votes






          active

          oldest

          votes









          3














          This looks to be an example of the optional chaining proposal, which is still very much a work in progress (only at Stage 1). It's not actually implemented in vanilla JS environments yet. Using



          obj?.prop


          means: if obj is undefined or null, the expression evaluates to undefined. But otherwise, it will evaluate to the prop property on the object. This is syntax sugar for



          obj && obj.prop


          (using just obj.prop alone will throw if obj is undefined or null)



          So, your



          abc?.xvy=== tyu?abc?.xz:abc?.xz


          will evaluate to true if the nested value abc?.xvy is equal to the nested value abc?.xz - or, it will evaluate to true if at least one of the nested values doesn't exist, and the other is undefined.



          Spaced out for easier reading:



          abc?.xvy === tyu
          
? abc?.xz
          
: abc?.xz


          As you can see, both ? and : expressions are the same, making the conditional operator unnecessary here. An equivalent test (assuming that referencing tyu doesn't throw) would be



          abc?.xvy === abc?.xz





          share|improve this answer




























            3














            This looks to be an example of the optional chaining proposal, which is still very much a work in progress (only at Stage 1). It's not actually implemented in vanilla JS environments yet. Using



            obj?.prop


            means: if obj is undefined or null, the expression evaluates to undefined. But otherwise, it will evaluate to the prop property on the object. This is syntax sugar for



            obj && obj.prop


            (using just obj.prop alone will throw if obj is undefined or null)



            So, your



            abc?.xvy=== tyu?abc?.xz:abc?.xz


            will evaluate to true if the nested value abc?.xvy is equal to the nested value abc?.xz - or, it will evaluate to true if at least one of the nested values doesn't exist, and the other is undefined.



            Spaced out for easier reading:



            abc?.xvy === tyu
            
? abc?.xz
            
: abc?.xz


            As you can see, both ? and : expressions are the same, making the conditional operator unnecessary here. An equivalent test (assuming that referencing tyu doesn't throw) would be



            abc?.xvy === abc?.xz





            share|improve this answer


























              3












              3








              3







              This looks to be an example of the optional chaining proposal, which is still very much a work in progress (only at Stage 1). It's not actually implemented in vanilla JS environments yet. Using



              obj?.prop


              means: if obj is undefined or null, the expression evaluates to undefined. But otherwise, it will evaluate to the prop property on the object. This is syntax sugar for



              obj && obj.prop


              (using just obj.prop alone will throw if obj is undefined or null)



              So, your



              abc?.xvy=== tyu?abc?.xz:abc?.xz


              will evaluate to true if the nested value abc?.xvy is equal to the nested value abc?.xz - or, it will evaluate to true if at least one of the nested values doesn't exist, and the other is undefined.



              Spaced out for easier reading:



              abc?.xvy === tyu
              
? abc?.xz
              
: abc?.xz


              As you can see, both ? and : expressions are the same, making the conditional operator unnecessary here. An equivalent test (assuming that referencing tyu doesn't throw) would be



              abc?.xvy === abc?.xz





              share|improve this answer













              This looks to be an example of the optional chaining proposal, which is still very much a work in progress (only at Stage 1). It's not actually implemented in vanilla JS environments yet. Using



              obj?.prop


              means: if obj is undefined or null, the expression evaluates to undefined. But otherwise, it will evaluate to the prop property on the object. This is syntax sugar for



              obj && obj.prop


              (using just obj.prop alone will throw if obj is undefined or null)



              So, your



              abc?.xvy=== tyu?abc?.xz:abc?.xz


              will evaluate to true if the nested value abc?.xvy is equal to the nested value abc?.xz - or, it will evaluate to true if at least one of the nested values doesn't exist, and the other is undefined.



              Spaced out for easier reading:



              abc?.xvy === tyu
              
? abc?.xz
              
: abc?.xz


              As you can see, both ? and : expressions are the same, making the conditional operator unnecessary here. An equivalent test (assuming that referencing tyu doesn't throw) would be



              abc?.xvy === abc?.xz






              share|improve this answer












              share|improve this answer



              share|improve this answer










              answered 28 mins ago









              CertainPerformanceCertainPerformance

              84.3k154169




              84.3k154169

























                  3














                  Its new ES proposal called "optionals" for safe check reading for object properties. Above expression is equivalent to:



                  (abc && abc.xvy) === (tyu) ? (abc && xz) : (abc && abc.xz)


                  You can find more details here: https://github.com/davidyaha/ecmascript-optionals-proposal






                  share|improve this answer






























                    3














                    Its new ES proposal called "optionals" for safe check reading for object properties. Above expression is equivalent to:



                    (abc && abc.xvy) === (tyu) ? (abc && xz) : (abc && abc.xz)


                    You can find more details here: https://github.com/davidyaha/ecmascript-optionals-proposal






                    share|improve this answer




























                      3












                      3








                      3







                      Its new ES proposal called "optionals" for safe check reading for object properties. Above expression is equivalent to:



                      (abc && abc.xvy) === (tyu) ? (abc && xz) : (abc && abc.xz)


                      You can find more details here: https://github.com/davidyaha/ecmascript-optionals-proposal






                      share|improve this answer















                      Its new ES proposal called "optionals" for safe check reading for object properties. Above expression is equivalent to:



                      (abc && abc.xvy) === (tyu) ? (abc && xz) : (abc && abc.xz)


                      You can find more details here: https://github.com/davidyaha/ecmascript-optionals-proposal







                      share|improve this answer














                      share|improve this answer



                      share|improve this answer








                      edited 24 mins ago

























                      answered 31 mins ago









                      Vishal RajoleVishal Rajole

                      796715




                      796715























                          2














                          It's called Null Propagation Operator.



                          We can think of each ?. operator as a short circuit where "if the expression up until this point is null or undefined, then the whole expression evaluates to undefined".
                          We could also optionally call functions.






                          share|improve this answer




























                            2














                            It's called Null Propagation Operator.



                            We can think of each ?. operator as a short circuit where "if the expression up until this point is null or undefined, then the whole expression evaluates to undefined".
                            We could also optionally call functions.






                            share|improve this answer


























                              2












                              2








                              2







                              It's called Null Propagation Operator.



                              We can think of each ?. operator as a short circuit where "if the expression up until this point is null or undefined, then the whole expression evaluates to undefined".
                              We could also optionally call functions.






                              share|improve this answer













                              It's called Null Propagation Operator.



                              We can think of each ?. operator as a short circuit where "if the expression up until this point is null or undefined, then the whole expression evaluates to undefined".
                              We could also optionally call functions.







                              share|improve this answer












                              share|improve this answer



                              share|improve this answer










                              answered 30 mins ago









                              Alex ParkAlex Park

                              312




                              312























                                  -1














                                  It is called the elvis operator



                                  It is a part of the ECMAScript proposals to make code more readable and reduce the long && chains



                                  essentially, it creates a short-circuit check for null or undefined and prevents the "Cannot read property of undefined" errors. If the value exists, the latter part is evaluated.



                                  You can read more here : Is there a null-coalescing (Elvis) operator or safe navigation operator in javascript?






                                  share|improve this answer






























                                    -1














                                    It is called the elvis operator



                                    It is a part of the ECMAScript proposals to make code more readable and reduce the long && chains



                                    essentially, it creates a short-circuit check for null or undefined and prevents the "Cannot read property of undefined" errors. If the value exists, the latter part is evaluated.



                                    You can read more here : Is there a null-coalescing (Elvis) operator or safe navigation operator in javascript?






                                    share|improve this answer




























                                      -1












                                      -1








                                      -1







                                      It is called the elvis operator



                                      It is a part of the ECMAScript proposals to make code more readable and reduce the long && chains



                                      essentially, it creates a short-circuit check for null or undefined and prevents the "Cannot read property of undefined" errors. If the value exists, the latter part is evaluated.



                                      You can read more here : Is there a null-coalescing (Elvis) operator or safe navigation operator in javascript?






                                      share|improve this answer















                                      It is called the elvis operator



                                      It is a part of the ECMAScript proposals to make code more readable and reduce the long && chains



                                      essentially, it creates a short-circuit check for null or undefined and prevents the "Cannot read property of undefined" errors. If the value exists, the latter part is evaluated.



                                      You can read more here : Is there a null-coalescing (Elvis) operator or safe navigation operator in javascript?







                                      share|improve this answer














                                      share|improve this answer



                                      share|improve this answer








                                      edited 2 mins ago

























                                      answered 16 mins ago









                                      Dhananjai PaiDhananjai Pai

                                      829113




                                      829113






























                                          draft saved

                                          draft discarded




















































                                          Thanks for contributing an answer to Stack Overflow!


                                          • Please be sure to answer the question. Provide details and share your research!

                                          But avoid …



                                          • Asking for help, clarification, or responding to other answers.

                                          • Making statements based on opinion; back them up with references or personal experience.


                                          To learn more, see our tips on writing great answers.




                                          draft saved


                                          draft discarded














                                          StackExchange.ready(
                                          function () {
                                          StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fstackoverflow.com%2fquestions%2f54528778%2fwhat-is-the-obj-prop-syntax-in-javascript%23new-answer', 'question_page');
                                          }
                                          );

                                          Post as a guest















                                          Required, but never shown





















































                                          Required, but never shown














                                          Required, but never shown












                                          Required, but never shown







                                          Required, but never shown

































                                          Required, but never shown














                                          Required, but never shown












                                          Required, but never shown







                                          Required, but never shown







                                          -

                                          Popular posts from this blog

                                          Bundesstraße 106

                                          Image
                                          Dieser Artikel beschreibt die Bundesstraße 106 in Deutschland. Zur gleichnamigen Straße in Österreich siehe Mölltal Straße. Vorlage:Infobox hochrangige Straße/Wartung/DE-B Bundesstraße 106 in Deutschland Karte Basisdaten Betreiber: Deutschland  Bundesrepublik Deutschland Straßenbeginn: Wismar ( 53° 54′  N , 11° 24′  O 53.900536 11.396875 ) Straßenende: Schwerin ( 53° 36′  N , 11° 24′  O 53.592785 11.404892 ) Gesamtlänge: 40,7 km Bundesland: Mecklenburg-Vorpommern Ausbauzustand: zweistreifig [1] Bundesstraße 106 in Schwerin (Umgehungsstraße) Straßenverlauf Land Mecklenburg-Vorpommern Landkreis Nordwestmecklenburg Ortsumgehung Wismar Wallensteingraben über   Dorf Mecklenburg Wallensteingraben Groß Stieten Bad Kleinen OT Niendorf Bahnstrecke Lübeck–Bad Kleinen Zickhusen Lübstorf Klein Trebbow OT Kirch Stück
                                          Read more

                                          Verónica Boquete

                                          Image
                                          Verónica Boquete im Trikot der Nationalmannschaft (2013) Personalia Name Verónica Boquete Giadans Geburtstag 9. April 1987 Geburtsort Santiago de Compostela, Spanien Größe 159 cm Position Mittelfeld / Sturm Juniorinnen Jahre Station 2001–2005 Xuventú Aguiño Frauen Jahre Station Spiele (Tore) 1 2005–2008 Prainsa Zaragoza 83 (40) 2008–2010 Espanyol Barcelona 53 (30) 2010 Buffalo Flash 9 0 (9) 2010 Chicago Red Stars 3 0 (1) 2010–2011 Espanyol Barcelona 26 (41) 2011 Philadelphia Independence 13 0 (5) 2011 Energija Woronesch 5 0 (1) 2012–2014 Tyresö FF 39 (14) 2014 Portland Thorns FC 15 0 (4) 2014–2015 1. FFC Frankfurt 23 0 (7) 2015–2016 FC Bayern München 9 0 (0) 2016–2018 Paris Saint-Germain 31 0 (8) 2018 Peking BG Phoenix 2019– Utah Royals FC 0 0 (0) Nationalmannschaft Jahre Auswahl
                                          Read more

                                          Ida-Boy-Ed-Garten

                                          Image
                                          Die Lage des Ida-Boy-Ed-Gartens, rot markiert Der Ida-Boy-Ed-Garten Der Ida-Boy-Ed-Garten, Blick von der Wakenitzmauer durch das Tor in der Stadtmauer Der Ida-Boy-Ed-Garten ist eine Straße der Lübecker Altstadt. Inhaltsverzeichnis 1 Lage 2 Geschichte 3 Literatur 4 Weblinks Lage | Der etwa 90 Meter lange Ida-Boy-Ed-Garten befindet sich an der nördlichen Spitze der Altstadtinsel, vor dem Burgtor. Die in einem Bogen durch eine Grünanlage hangaufwärts führende Straße verbindet die Wakenitzmauer mit der Burgtorbrücke. Geschichte | Der heutige Ida-Boy-Ed-Garten wurde ursprünglich als Verlängerung der Wakenitzmauer angelegt. 1903 wurde in den erhaltenen Teil der mittelalterlichen Stadtmauer, an dem die Wakenitzmauer bei der Einmündung der Kaiserstraße begann, ein Tor mit einem großen Bogen für die Durchführung der Straße und zwei kleineren seitlichen Öffnungen für Fußgänger gebrochen, um für die neu errichteten Wohnhäuser in diesem Bereich
                                          Read more