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
    18 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
    18 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 11 mins ago









adiga

7,96962141




7,96962141










asked 28 mins ago









Apurva PathakApurva Pathak

1049




1049













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

    – adiga
    18 mins ago



















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

    – adiga
    18 mins ago

















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

– adiga
18 mins ago





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

– adiga
18 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 18 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 20 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 14 mins ago

























                              answered 21 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 6 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

                                          How to label and detect the document text images

                                          Image
                                          1 $begingroup$ This is what I mean as document text image: I want to label the texts in image as separate blocks and my model should detect these labels as classes. NOTE: This is how the end result should be like: The labels like Block 1, Block 2, Block 3,.. should be Logo, Title, Date,.. Others, etc. Work done: First approach : I tried to implement this method via Object Detection, it didn't work. It didn't even detect any text. Second approach : Then I tried it using PixelLink. As this model is build for scene text detection, it detected each and every text in the image. But this method can detect multiple lines of text if the threshold values are increased. But I have no idea how do I add labels to the text blocks. PIXEL_CLS_WEIGHT_all_ones = 'PIXEL_CLS_WEIGHT_all_ones' PIXEL_C...
                                          Read more

                                          Vallis Paradisi

                                          Image
                                          Coordinata: .mw-parser-output .geo-default,.mw-parser-output .geo-dms,.mw-parser-output .geo-dec{display:inline}.mw-parser-output .geo-nondefault,.mw-parser-output .geo-multi-punct{display:none}.mw-parser-output .longitude,.mw-parser-output .latitude{white-space:nowrap} 33°03′S 71°37′W  /  33.05°S 71.617°W  / -33.05; -71.617 Vallis Paradisi Res apud Vicidata repertae: Civitas : Chilia Numerus incolarum : 296 655 Zona horaria : UTC-4 Situs interretialis Nomen officiale : Valparaíso Gubernium Consilium : municipal council of Valparaíso Geographia Superficies : 401 600 000 Metrum quadratum Coniunctiones urbium Urbes gemellae : Ovetum , Badalona , Santa Fe , Ora longa , Sciamhaevum , Quantunia , Callao , Bat Yam , Melaka , Novorossiysk , Busan , Corduba , Odessa , Rosario , Malacca , Barcino , Soteropolis , Franciscopolis (California) , Guanajuato, Silao Tabula aut despectus Despectus in portum sinumque et urbem Vallis Paradisi Vallis Para...
                                          Read more

                                          Tabula Rosettana

                                          Image
                                          Tabula multilinguis Rosettana in Museo Britannico ostenditur. Tabula Rosettana, [1] etiam titulo OGIS 90 agnita, est stela decreto de rebus sacris in Aegypto anno 196 a.C.n. lato inscripta. Tabula iuxta Rosettam Aegypti, urbem in delta Nili et ad oram maris Mediterranei iacentem, anno 1799 a milite Francico reperta est. Inventio stelae, linguis duabus scripturisque tribus inscriptae, eruditis Instituti Aegypti statim nuntiata est; ibi enim iussu imperatoris Napoleonis eruditi omnium scientiarum (sub aegide Commissionis Scientiarum et Artium) properaverant cum expeditione Francica. Qua a Britannis mox debellata, tabula Rosettana Londinium missa hodie apud Museum Britannicum iacet. Textus Graecus cito lectus interpretationi textuum Aegyptiorum (in formis hieroglyphica et demotica expressorum) gradatim adiuvit. Denique textum plene interpretatus est Ioannes Franciscus Champollion. Ab opere eruditorum cumulativo coepit hodiernus scripturae hieroglyphicae linguaeque Aegyptiae a...
                                          Read more