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Javascript Falsy Check execution order in an IF condition
The 2019 Stack Overflow Developer Survey Results Are InJavaScript check if variable exists (is defined/initialized)How do JavaScript closures work?How do I check if an element is hidden in jQuery?How do I remove a property from a JavaScript object?How do I check if an array includes an object in JavaScript?Which equals operator (== vs ===) should be used in JavaScript comparisons?Setting “checked” for a checkbox with jQuery?How do I include a JavaScript file in another JavaScript file?What does “use strict” do in JavaScript, and what is the reasoning behind it?How to check whether a string contains a substring in JavaScript?How do I remove a particular element from an array in JavaScript?
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I have a program that calls a back-end service and collects a response. It is collected as follows. We destructure the response object and get the Error and Data.
const data, error = response;
If there is no error, the Error object becomes null. Consider the following two options.
Option One:
if (!error)
// handle error
Option Two:
if (error !== null)
// handle error
In Option One, As per this answer, the following conditions are checked.
undefined: if the value is not defined and it's undefined
null: if it's null, for example, if a DOM element not exists...
empty string: ''
0: number zero
NaN: not a number- false
Is there an order of execution when we call Option 1? How does the internal condition checking happen in Option 1? Based on this, will there be a performance impact (in a granular level), if we use Option 1 instead of Option 2?
javascript
asked Mar 8 at 8:51
Keet SugathadasaKeet Sugathadasa
725621
|
show 5 more comments
I have a program that calls a back-end service and collects a response. It is collected as follows. We destructure the response object and get the Error and Data.
const data, error = response;
If there is no error, the Error object becomes null. Consider the following two options.
Option One:
if (!error)
// handle error
Option Two:
if (error !== null)
// handle error
In Option One, As per this answer, the following conditions are checked.
undefined: if the value is not defined and it's undefined
null: if it's null, for example, if a DOM element not exists...
empty string: ''
0: number zero
NaN: not a number- false
Is there an order of execution when we call Option 1? How does the internal condition checking happen in Option 1? Based on this, will there be a performance impact (in a granular level), if we use Option 1 instead of Option 2?
javascript
asked Mar 8 at 8:51
Keet SugathadasaKeet Sugathadasa
725621
5
async vs speed of a micro optimization? really?
– Nina Scholz
Mar 8 at 8:53
1
Also I think you mean something else thanif (!error) // handle error
– mplungjan
Mar 8 at 8:56
3
This must be the most micro of premature optimisations I've ever seen.
– VLAZ
Mar 8 at 8:58
Interestingly the destructuring assignment is probably the slowest part in this example...
– Yoshi
Mar 8 at 9:02
I agree that it's a very micro level optimization. This came up in a Git Pull Request comment. Could I know the reason for downvotes?
– Keet Sugathadasa
Mar 8 at 9:04
|
show 5 more comments
I have a program that calls a back-end service and collects a response. It is collected as follows. We destructure the response object and get the Error and Data.
const data, error = response;
If there is no error, the Error object becomes null. Consider the following two options.
Option One:
if (!error)
// handle error
Option Two:
if (error !== null)
// handle error
In Option One, As per this answer, the following conditions are checked.
undefined: if the value is not defined and it's undefined
null: if it's null, for example, if a DOM element not exists...
empty string: ''
0: number zero
NaN: not a number- false
Is there an order of execution when we call Option 1? How does the internal condition checking happen in Option 1? Based on this, will there be a performance impact (in a granular level), if we use Option 1 instead of Option 2?
javascript
asked Mar 8 at 8:51
Keet SugathadasaKeet Sugathadasa
725621
I have a program that calls a back-end service and collects a response. It is collected as follows. We destructure the response object and get the Error and Data.
const data, error = response;
If there is no error, the Error object becomes null. Consider the following two options.
Option One:
if (!error)
// handle error
Option Two:
if (error !== null)
// handle error
In Option One, As per this answer, the following conditions are checked.
undefined: if the value is not defined and it's undefined
null: if it's null, for example, if a DOM element not exists...
empty string: ''
0: number zero
NaN: not a number- false
Is there an order of execution when we call Option 1? How does the internal condition checking happen in Option 1? Based on this, will there be a performance impact (in a granular level), if we use Option 1 instead of Option 2?
javascript
javascript
asked Mar 8 at 8:51
Keet SugathadasaKeet Sugathadasa
725621
asked Mar 8 at 8:51
Keet SugathadasaKeet Sugathadasa
725621
asked Mar 8 at 8:51
Keet SugathadasaKeet Sugathadasa
725621
asked Mar 8 at 8:51
Keet SugathadasaKeet Sugathadasa
725621
asked Mar 8 at 8:51
Keet SugathadasaKeet Sugathadasa
725621
725621
5
async vs speed of a micro optimization? really?
– Nina Scholz
Mar 8 at 8:53
1
Also I think you mean something else thanif (!error) // handle error
– mplungjan
Mar 8 at 8:56
3
This must be the most micro of premature optimisations I've ever seen.
– VLAZ
Mar 8 at 8:58
Interestingly the destructuring assignment is probably the slowest part in this example...
– Yoshi
Mar 8 at 9:02
I agree that it's a very micro level optimization. This came up in a Git Pull Request comment. Could I know the reason for downvotes?
– Keet Sugathadasa
Mar 8 at 9:04
|
show 5 more comments
5
async vs speed of a micro optimization? really?
– Nina Scholz
Mar 8 at 8:53
1
Also I think you mean something else thanif (!error) // handle error
– mplungjan
Mar 8 at 8:56
3
This must be the most micro of premature optimisations I've ever seen.
– VLAZ
Mar 8 at 8:58
Interestingly the destructuring assignment is probably the slowest part in this example...
– Yoshi
Mar 8 at 9:02
I agree that it's a very micro level optimization. This came up in a Git Pull Request comment. Could I know the reason for downvotes?
– Keet Sugathadasa
Mar 8 at 9:04
5
5
async vs speed of a micro optimization? really?
– Nina Scholz
Mar 8 at 8:53
async vs speed of a micro optimization? really?
– Nina Scholz
Mar 8 at 8:53
1
1
Also I think you mean something else than
if (!error) // handle error – mplungjan
Mar 8 at 8:56
Also I think you mean something else than
if (!error) // handle error – mplungjan
Mar 8 at 8:56
3
3
This must be the most micro of premature optimisations I've ever seen.
– VLAZ
Mar 8 at 8:58
This must be the most micro of premature optimisations I've ever seen.
– VLAZ
Mar 8 at 8:58
Interestingly the destructuring assignment is probably the slowest part in this example...
– Yoshi
Mar 8 at 9:02
Interestingly the destructuring assignment is probably the slowest part in this example...
– Yoshi
Mar 8 at 9:02
I agree that it's a very micro level optimization. This came up in a Git Pull Request comment. Could I know the reason for downvotes?
– Keet Sugathadasa
Mar 8 at 9:04
I agree that it's a very micro level optimization. This came up in a Git Pull Request comment. Could I know the reason for downvotes?
– Keet Sugathadasa
Mar 8 at 9:04
|
show 5 more comments
1 Answer
1
active
oldest
votes
There is no order in this usage of if statement, JS just performs type conversion to coerce any value to boolean and then evaluates the result, check this link for more details: https://developer.mozilla.org/en-US/docs/Glossary/Falsy
Falsey results:
if (false)
if (null)
if (undefined)
if (0)
if (NaN)
if ('')
if ("")
if (``)
if (document.all)
// => false
Truthy results:
if (true)
if ()
if ([])
if (42)
if ("foo")
if new Date())
if (-42)
if (3.14)
if (-3.14)
if (Infinity)
if (-Infinity)
// => true
answered Mar 8 at 8:58
Branislav PopadičBranislav Popadič
214
add a comment |
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1 Answer
1
active
oldest
votes
1 Answer
1
active
oldest
votes
active
oldest
votes
active
oldest
votes
There is no order in this usage of if statement, JS just performs type conversion to coerce any value to boolean and then evaluates the result, check this link for more details: https://developer.mozilla.org/en-US/docs/Glossary/Falsy
Falsey results:
if (false)
if (null)
if (undefined)
if (0)
if (NaN)
if ('')
if ("")
if (``)
if (document.all)
// => false
Truthy results:
if (true)
if ()
if ([])
if (42)
if ("foo")
if new Date())
if (-42)
if (3.14)
if (-3.14)
if (Infinity)
if (-Infinity)
// => true
answered Mar 8 at 8:58
Branislav PopadičBranislav Popadič
214
add a comment |
There is no order in this usage of if statement, JS just performs type conversion to coerce any value to boolean and then evaluates the result, check this link for more details: https://developer.mozilla.org/en-US/docs/Glossary/Falsy
Falsey results:
if (false)
if (null)
if (undefined)
if (0)
if (NaN)
if ('')
if ("")
if (``)
if (document.all)
// => false
Truthy results:
if (true)
if ()
if ([])
if (42)
if ("foo")
if new Date())
if (-42)
if (3.14)
if (-3.14)
if (Infinity)
if (-Infinity)
// => true
answered Mar 8 at 8:58
Branislav PopadičBranislav Popadič
214
add a comment |
There is no order in this usage of if statement, JS just performs type conversion to coerce any value to boolean and then evaluates the result, check this link for more details: https://developer.mozilla.org/en-US/docs/Glossary/Falsy
Falsey results:
if (false)
if (null)
if (undefined)
if (0)
if (NaN)
if ('')
if ("")
if (``)
if (document.all)
// => false
Truthy results:
if (true)
if ()
if ([])
if (42)
if ("foo")
if new Date())
if (-42)
if (3.14)
if (-3.14)
if (Infinity)
if (-Infinity)
// => true
answered Mar 8 at 8:58
Branislav PopadičBranislav Popadič
214
There is no order in this usage of if statement, JS just performs type conversion to coerce any value to boolean and then evaluates the result, check this link for more details: https://developer.mozilla.org/en-US/docs/Glossary/Falsy
Falsey results:
if (false)
if (null)
if (undefined)
if (0)
if (NaN)
if ('')
if ("")
if (``)
if (document.all)
// => false
Truthy results:
if (true)
if ()
if ([])
if (42)
if ("foo")
if new Date())
if (-42)
if (3.14)
if (-3.14)
if (Infinity)
if (-Infinity)
// => true
answered Mar 8 at 8:58
Branislav PopadičBranislav Popadič
214
edited Mar 8 at 9:04
answered Mar 8 at 8:58
Branislav PopadičBranislav Popadič
214
answered Mar 8 at 8:58
Branislav PopadičBranislav Popadič
214
answered Mar 8 at 8:58
Branislav PopadičBranislav Popadič
214
214
add a comment |
add a comment |
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5
async vs speed of a micro optimization? really?
– Nina Scholz
Mar 8 at 8:53
1
Also I think you mean something else than
if (!error) // handle error– mplungjan
Mar 8 at 8:56
3
This must be the most micro of premature optimisations I've ever seen.
– VLAZ
Mar 8 at 8:58
Interestingly the destructuring assignment is probably the slowest part in this example...
– Yoshi
Mar 8 at 9:02
I agree that it's a very micro level optimization. This came up in a Git Pull Request comment. Could I know the reason for downvotes?
– Keet Sugathadasa
Mar 8 at 9:04