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. I know that it is Null-safe property access but I am bit confused about the chaining.
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
    40 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. I know that it is Null-safe property access but I am bit confused about the chaining.
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
    40 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. I know that it is Null-safe property access but I am bit confused about the chaining.
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. I know that it is Null-safe property access but I am bit confused about the chaining.
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 2 mins ago







Apurva Pathak

















asked 50 mins ago









Apurva PathakApurva Pathak

1069




1069













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

    – adiga
    40 mins ago



















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

    – adiga
    40 mins ago

















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

– adiga
40 mins ago





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

– adiga
40 mins ago












4 Answers
4






active

oldest

votes


















4














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

































    4














    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














      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

























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          4 Answers
          4






          active

          oldest

          votes








          4 Answers
          4






          active

          oldest

          votes









          active

          oldest

          votes






          active

          oldest

          votes









          4














          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






























            4














            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




























              4












              4








              4







              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 36 mins ago

























              answered 43 mins ago









              Vishal RajoleVishal Rajole

              821715




              821715

























                  4














                  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




























                    4














                    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


























                      4












                      4








                      4







                      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 40 mins ago









                      CertainPerformanceCertainPerformance

                      84.3k154169




                      84.3k154169























                          3














                          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




























                            3














                            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


























                              3












                              3








                              3







                              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 42 mins ago









                              Alex ParkAlex Park

                              412




                              412























                                  -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 14 mins ago

























                                      answered 28 mins ago









                                      Dhananjai PaiDhananjai Pai

                                      829113




                                      829113






























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