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
    16 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
    16 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 10 mins ago









adiga

7,96962141




7,96962141










asked 26 mins ago









Apurva PathakApurva Pathak

1049




1049













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

    – adiga
    16 mins ago



















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

    – adiga
    16 mins ago

















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

– adiga
16 mins ago





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

– adiga
16 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































    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














      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

































        0














        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.





        share























          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 16 mins ago









              CertainPerformanceCertainPerformance

              84.3k154169




              84.3k154169

























                  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 18 mins ago









                      Alex ParkAlex Park

                      312




                      312























                          2














                          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














                            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












                              2








                              2







                              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 12 mins ago

























                              answered 19 mins ago









                              Vishal RajoleVishal Rajole

                              786715




                              786715























                                  0














                                  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.





                                  share




























                                    0














                                    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.





                                    share


























                                      0












                                      0








                                      0







                                      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.





                                      share













                                      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.






                                      share











                                      share


                                      share










                                      answered 5 mins ago









                                      Dhananjai PaiDhananjai Pai

                                      831113




                                      831113






























                                          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

                                          flock() on closed filehandle LOCK_FILE at /usr/bin/apt-mirror

                                          Image
                                          0 I recently upgraded an Ubuntu 16.04 virtual machine to 18.04. I regularly use this VM to run apt-mirror at school on their high-speed internet, then rsync these files to my rack-mount server at home for updating multiple computers at home without wasting the tiny amount of bandwidth I have there. Since updating I can't get apt-mirror to run on my VM. It keeps giving the error: flock() on closed filehandle LOCK_FILE at /usr/bin/apt-mirror line 214 immediately followed by: apt-mirror is already running, exiting at /usr/bin/apt-mirror line 217 apt-mirror is NOT running, and does not have a cron job. I've tried rebooting, and even looked for the old-style lockfile to delete, but I guess that method is no longer used. Is there some way to force unlock this so I can run apt-mirror? UPDATE: So... I f
                                          Read more

                                          Mangá

                                          Image
                                            Nota:  Não confundir com Manga. Mangás e Animes Mangá Mangaká • Tankōbon Film comic La nouvelle manga Mangá original em inglês Anime História Animação influenciada por animes • Filler • OVA • Seiyū Públicos Kodomo • Shōjo • Shōnen Josei • Seinen Gêneros Mahō shōjo • Mecha • Harém Ecchi • Hentai ( Yaoi • Yuri Futanari • Shotacon • Lolicon Toddlercon ) Termos Bishōjo • Chibi • Fan service Gaiden • Kawaii • Kaitō • Light novel Mahō shōnen • Moe (antropomorfismo • Kemonomimi Nekomimi ) • Super deformed Omake • Tsundere • Yonkoma Listas Mangás • Animes • Ecchi • Mangaka • Estúdios • Revistas Fãs ( otaku ) Anime Music Video Convenções • Cosplay Dōjinshi • Fansub • Fandub • Fujoshi OS-tan • Scanlation Portal de Anime e mangá v d e O mangá (português brasileiro) ou manga (português europeu) [ 1 ] (em japonês: 漫画 , manga ? , lit. “história em quadrinhos”) , é a
                                          Read more

                                           ⁒  ․,‪⁊‑⁙ ⁖, ⁇‒※‌, †,⁖‗‌⁝    ‾‸⁘,‖⁔⁣,⁂‾
”‑,‥–,‬ ,⁀‹⁋‴⁑ ‒ ,‴⁋”‼ ⁨,‷⁔„ ‰′,‐‚ ‥‡‎“‷⁃⁨⁅⁣,⁔
⁇‘⁔⁡⁏⁌⁡‿‶‏⁨ ⁣⁕⁖⁨⁩⁥‽⁀  ‴‬⁜‟ ⁃‣‧⁕‮ …‍⁨‴ ⁩,⁚⁖‫ ,‵ ⁀,‮⁝‣‣ ⁑  ⁂– ․, ‾‽ ‏⁁“⁗‸ ‾… ‹‡⁌⁎‸‘ ‡⁏⁌‪ ‵⁛ ‎⁨ ―⁦⁤⁄⁕

                                          ⁉…‧ ⁩,“⁡‹⁃‽⁞•,⁠‚  ⁓⁎  ⁜ ‴ ⁥⁡⁎‭,‍‑⁁⁌⁦ ⁁‟⁙‥‒“⁈ ,‪⁧ ⁙‿⁇⁦,⁝‘ ⁎“⁘‫‪,‗‹‛‹⁒  ⁇⁄‗‒•“⁇   ‐ ⁂
‘‛, ‶⁦ ⁇ ​⁞‧ 
,⁏ …‹–⁗⁡⁘⁄ ‏‿‬‟″ ‏⁢⁦⁗⁚⁝‬⁢⁏,⁧″⁍′‖⁂※⁄‘– ‵⁡ ‭⁢⁚,⁅‧,‼‛⁗,⁡⁗“⁔⁃⁍‷⁏‗‱⁌‚  
•⁝ ‚‒ ‥‰  ′⁌, ⁄, ⁛—‭‑”⁂,⁑ ‡⁨‴⁖⁙…,‑, ,⁎,․‣‥  ‴‎⁎,″‛⁎‭‿ ⁤ ‷‾‼‖,⁠⁊‾,⁦“‗‑‌†,⁙,†⁝′ 
,―‚․‘, ⁢  ‿‌,⁀„‣,⁌,‭‖ ⁆“‪,―  ⁀ ⁃,
‷⁥,​,‟‗⁄⁉⁐⁗―
,‮⁢⁩⁆⁣‹‭⁅ ⁝‾‏‭⁖ ⁕⁄‷,†‟‒ ⁣‹,​…​,⁤⁂⁨‮⁎⁙–‟‼ ⁍‱‱,‽,‫‽‣ ⁒,⁨ ⁄ ⁝”„‿‑‎⁈‿
 ⁀‛‼‟ ⁑“,⁩​ ‒
–⁡…⁢ ⁂ ⁈⁎,‵‡,⁛,,‱⁧⁋,․‬⁄ “,⁄‴⁊  ‗―,‵⁙⁔—⁀ —  ⁀‬‬ ‒⁋‼⁀― ,⁌′ ‍‶ ’
                                          Read more