What is the obj?.prop syntax in javascript?
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
edited 10 mins ago
adiga
7,96962141
asked 26 mins ago
Apurva PathakApurva Pathak
1049
add a comment |
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
edited 10 mins ago
adiga
7,96962141
asked 26 mins ago
Apurva PathakApurva Pathak
1049
Possible duplicate of Null-safe property access (and conditional assignment) in ES6/2015
– adiga
16 mins ago
add a comment |
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
edited 10 mins ago
adiga
7,96962141
asked 26 mins ago
Apurva PathakApurva Pathak
1049
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
edited 10 mins ago
adiga
7,96962141
asked 26 mins ago
Apurva PathakApurva Pathak
1049
edited 10 mins ago
adiga
7,96962141
asked 26 mins ago
Apurva PathakApurva Pathak
1049
edited 10 mins ago
adiga
7,96962141
edited 10 mins ago
adiga
7,96962141
edited 10 mins ago
adiga
7,96962141
7,96962141
asked 26 mins ago
Apurva PathakApurva Pathak
1049
asked 26 mins ago
Apurva PathakApurva Pathak
1049
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
add a comment |
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
add a comment |
4 Answers
4
active
oldest
votes
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
answered 16 mins ago
CertainPerformanceCertainPerformance
84.3k154169
add a comment |
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.
answered 18 mins ago
Alex ParkAlex Park
312
add a comment |
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
answered 19 mins ago
Vishal RajoleVishal Rajole
786715
add a comment |
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.
answered 5 mins ago
Dhananjai PaiDhananjai Pai
831113
add a comment |
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4 Answers
4
active
oldest
votes
4 Answers
4
active
oldest
votes
active
oldest
votes
active
oldest
votes
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
answered 16 mins ago
CertainPerformanceCertainPerformance
84.3k154169
add a comment |
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
answered 16 mins ago
CertainPerformanceCertainPerformance
84.3k154169
add a comment |
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
answered 16 mins ago
CertainPerformanceCertainPerformance
84.3k154169
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
answered 16 mins ago
CertainPerformanceCertainPerformance
84.3k154169
answered 16 mins ago
CertainPerformanceCertainPerformance
84.3k154169
answered 16 mins ago
CertainPerformanceCertainPerformance
84.3k154169
answered 16 mins ago
CertainPerformanceCertainPerformance
84.3k154169
84.3k154169
add a comment |
add a comment |
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.
answered 18 mins ago
Alex ParkAlex Park
312
add a comment |
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.
answered 18 mins ago
Alex ParkAlex Park
312
add a comment |
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.
answered 18 mins ago
Alex ParkAlex Park
312
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.
answered 18 mins ago
Alex ParkAlex Park
312
answered 18 mins ago
Alex ParkAlex Park
312
answered 18 mins ago
Alex ParkAlex Park
312
answered 18 mins ago
Alex ParkAlex Park
312
312
add a comment |
add a comment |
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
answered 19 mins ago
Vishal RajoleVishal Rajole
786715
add a comment |
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
answered 19 mins ago
Vishal RajoleVishal Rajole
786715
add a comment |
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
answered 19 mins ago
Vishal RajoleVishal Rajole
786715
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
answered 19 mins ago
Vishal RajoleVishal Rajole
786715
edited 12 mins ago
answered 19 mins ago
Vishal RajoleVishal Rajole
786715
answered 19 mins ago
Vishal RajoleVishal Rajole
786715
answered 19 mins ago
Vishal RajoleVishal Rajole
786715
786715
add a comment |
add a comment |
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.
answered 5 mins ago
Dhananjai PaiDhananjai Pai
831113
add a comment |
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.
answered 5 mins ago
Dhananjai PaiDhananjai Pai
831113
add a comment |
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.
answered 5 mins ago
Dhananjai PaiDhananjai Pai
831113
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.
answered 5 mins ago
Dhananjai PaiDhananjai Pai
831113
answered 5 mins ago
Dhananjai PaiDhananjai Pai
831113
answered 5 mins ago
Dhananjai PaiDhananjai Pai
831113
answered 5 mins ago
Dhananjai PaiDhananjai Pai
831113
831113
add a comment |
add a comment |
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Possible duplicate of Null-safe property access (and conditional assignment) in ES6/2015
– adiga
16 mins ago