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
    22 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
    22 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 16 mins ago









adiga

7,96962141




7,96962141










asked 32 mins ago









Apurva PathakApurva Pathak

1049




1049













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

    – adiga
    22 mins ago



















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

    – adiga
    22 mins ago

















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

– adiga
22 mins ago





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

– adiga
22 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































        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|improve this answer























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          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 22 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 18 mins ago

























                      answered 25 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 24 mins ago









                              Alex ParkAlex Park

                              312




                              312























                                  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|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|improve this answer


























                                      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|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.







                                      share|improve this answer












                                      share|improve this answer



                                      share|improve this answer










                                      answered 10 mins ago









                                      Dhananjai PaiDhananjai Pai

                                      831113




                                      831113






























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