Why Array.filter(Number) filters zero out in javascript?
I'm trying to filter all non-numeric out from array. We can see desired output when using typeof. But with Number, it filters zero out.
Here's the example (tested in Chrome Console):
[-1, 0, 1, 2, 3, 4, Number(0), '', 'test'].filter(Number)
// Which output with zero filtered out:
[-1, 1, 2, 3, 4] // 0 is filtered
If we use type of, it doesn't filter zero, which was expected
// code
[-1, 0, 1, 2, 3, 4, Number(0), '', 'test'].filter(n => typeof n === 'number')
// output
[-1, 0, 1, 2, 3, 4, 0]
My question:
What is the difference between the 'Number' and 'type of' approach?
Number filter zero, but 'Number' itself literally containing zero, and this makes me confusing.
javascript numbers typeof
asked 1 hour ago
imckl
433
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imckl is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
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add a comment |
I'm trying to filter all non-numeric out from array. We can see desired output when using typeof. But with Number, it filters zero out.
Here's the example (tested in Chrome Console):
[-1, 0, 1, 2, 3, 4, Number(0), '', 'test'].filter(Number)
// Which output with zero filtered out:
[-1, 1, 2, 3, 4] // 0 is filtered
If we use type of, it doesn't filter zero, which was expected
// code
[-1, 0, 1, 2, 3, 4, Number(0), '', 'test'].filter(n => typeof n === 'number')
// output
[-1, 0, 1, 2, 3, 4, 0]
My question:
What is the difference between the 'Number' and 'type of' approach?
Number filter zero, but 'Number' itself literally containing zero, and this makes me confusing.
javascript numbers typeof
asked 1 hour ago
imckl
433
New contributor
imckl is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
add a comment |
I'm trying to filter all non-numeric out from array. We can see desired output when using typeof. But with Number, it filters zero out.
Here's the example (tested in Chrome Console):
[-1, 0, 1, 2, 3, 4, Number(0), '', 'test'].filter(Number)
// Which output with zero filtered out:
[-1, 1, 2, 3, 4] // 0 is filtered
If we use type of, it doesn't filter zero, which was expected
// code
[-1, 0, 1, 2, 3, 4, Number(0), '', 'test'].filter(n => typeof n === 'number')
// output
[-1, 0, 1, 2, 3, 4, 0]
My question:
What is the difference between the 'Number' and 'type of' approach?
Number filter zero, but 'Number' itself literally containing zero, and this makes me confusing.
javascript numbers typeof
asked 1 hour ago
imckl
433
New contributor
imckl is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
I'm trying to filter all non-numeric out from array. We can see desired output when using typeof. But with Number, it filters zero out.
Here's the example (tested in Chrome Console):
[-1, 0, 1, 2, 3, 4, Number(0), '', 'test'].filter(Number)
// Which output with zero filtered out:
[-1, 1, 2, 3, 4] // 0 is filtered
If we use type of, it doesn't filter zero, which was expected
// code
[-1, 0, 1, 2, 3, 4, Number(0), '', 'test'].filter(n => typeof n === 'number')
// output
[-1, 0, 1, 2, 3, 4, 0]
My question:
What is the difference between the 'Number' and 'type of' approach?
Number filter zero, but 'Number' itself literally containing zero, and this makes me confusing.
javascript numbers typeof
javascript numbers typeof
asked 1 hour ago
imckl
433
New contributor
imckl is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
asked 1 hour ago
imckl
433
New contributor
imckl is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
asked 1 hour ago
imckl
433
New contributor
imckl is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
asked 1 hour ago
imckl
433
asked 1 hour ago
imckl
433
433
New contributor
imckl is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
New contributor
imckl is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
imckl is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
add a comment |
add a comment |
4 Answers
4
active
oldest
votes
Because 0 is one of the many falsy values in javascript
All these conditions will be sent to else blocks:
if (false)
if (null)
if (undefined)
if (0)
if (NaN)
if ('')
if ("")
if (``)
From the Array.prototype.filter() documentation:
filter()calls a providedcallbackfunction once for each element in an array, and constructs a new array of all the values for which callback returns a value that coerces to true
In your case the callback function is the Number. So your code is equivalent to:
[-1, 0, 1, 2, 3, 4, Number(0), '', 'test'].filter(a => Number(a))
answered 1 hour ago
adiga
5,64361938
Thanks for the detailed explanation! Marked as accepted :)
– imckl
1 hour ago
add a comment |
Zero is a falsey value. The typeof is always returning a boolean value. When the number 0 is returned, it is returning to the test, and therefore coming back as false, so the number zero is filtered out.
answered 1 hour ago
bronkula
287
add a comment |
When you're using Number in filter, Actually it is passing each item of Array to Number constructor and in case of string or 0 Number will return NaN or 0 and both of them are false so filter is filtering out both of them
whereas when you're using typeof then 0 has "number" type so it is returning true and filter method doesn't filtering it out
answered 1 hour ago
Abhay Sehgal
16318
1
This answer with @adiga falsy explanation solves my confusing :)
– imckl
1 hour ago
add a comment |
It's because 0 is a falsy value which returns false
Documentation
https://developer.mozilla.org/en-US/docs/Glossary/Falsy
answered 1 hour ago
AnonymousSB
2,149220
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
Because 0 is one of the many falsy values in javascript
All these conditions will be sent to else blocks:
if (false)
if (null)
if (undefined)
if (0)
if (NaN)
if ('')
if ("")
if (``)
From the Array.prototype.filter() documentation:
filter()calls a providedcallbackfunction once for each element in an array, and constructs a new array of all the values for which callback returns a value that coerces to true
In your case the callback function is the Number. So your code is equivalent to:
[-1, 0, 1, 2, 3, 4, Number(0), '', 'test'].filter(a => Number(a))
answered 1 hour ago
adiga
5,64361938
Thanks for the detailed explanation! Marked as accepted :)
– imckl
1 hour ago
add a comment |
Because 0 is one of the many falsy values in javascript
All these conditions will be sent to else blocks:
if (false)
if (null)
if (undefined)
if (0)
if (NaN)
if ('')
if ("")
if (``)
From the Array.prototype.filter() documentation:
filter()calls a providedcallbackfunction once for each element in an array, and constructs a new array of all the values for which callback returns a value that coerces to true
In your case the callback function is the Number. So your code is equivalent to:
[-1, 0, 1, 2, 3, 4, Number(0), '', 'test'].filter(a => Number(a))
answered 1 hour ago
adiga
5,64361938
Thanks for the detailed explanation! Marked as accepted :)
– imckl
1 hour ago
add a comment |
Because 0 is one of the many falsy values in javascript
All these conditions will be sent to else blocks:
if (false)
if (null)
if (undefined)
if (0)
if (NaN)
if ('')
if ("")
if (``)
From the Array.prototype.filter() documentation:
filter()calls a providedcallbackfunction once for each element in an array, and constructs a new array of all the values for which callback returns a value that coerces to true
In your case the callback function is the Number. So your code is equivalent to:
[-1, 0, 1, 2, 3, 4, Number(0), '', 'test'].filter(a => Number(a))
answered 1 hour ago
adiga
5,64361938
Because 0 is one of the many falsy values in javascript
All these conditions will be sent to else blocks:
if (false)
if (null)
if (undefined)
if (0)
if (NaN)
if ('')
if ("")
if (``)
From the Array.prototype.filter() documentation:
filter()calls a providedcallbackfunction once for each element in an array, and constructs a new array of all the values for which callback returns a value that coerces to true
In your case the callback function is the Number. So your code is equivalent to:
[-1, 0, 1, 2, 3, 4, Number(0), '', 'test'].filter(a => Number(a))
answered 1 hour ago
adiga
5,64361938
edited 1 hour ago
answered 1 hour ago
adiga
5,64361938
answered 1 hour ago
adiga
5,64361938
answered 1 hour ago
adiga
5,64361938
5,64361938
Thanks for the detailed explanation! Marked as accepted :)
– imckl
1 hour ago
add a comment |
Thanks for the detailed explanation! Marked as accepted :)
– imckl
1 hour ago
Thanks for the detailed explanation! Marked as accepted :)
– imckl
1 hour ago
Thanks for the detailed explanation! Marked as accepted :)
– imckl
1 hour ago
add a comment |
Zero is a falsey value. The typeof is always returning a boolean value. When the number 0 is returned, it is returning to the test, and therefore coming back as false, so the number zero is filtered out.
answered 1 hour ago
bronkula
287
add a comment |
Zero is a falsey value. The typeof is always returning a boolean value. When the number 0 is returned, it is returning to the test, and therefore coming back as false, so the number zero is filtered out.
answered 1 hour ago
bronkula
287
add a comment |
Zero is a falsey value. The typeof is always returning a boolean value. When the number 0 is returned, it is returning to the test, and therefore coming back as false, so the number zero is filtered out.
answered 1 hour ago
bronkula
287
Zero is a falsey value. The typeof is always returning a boolean value. When the number 0 is returned, it is returning to the test, and therefore coming back as false, so the number zero is filtered out.
answered 1 hour ago
bronkula
287
answered 1 hour ago
bronkula
287
answered 1 hour ago
bronkula
287
answered 1 hour ago
bronkula
287
287
add a comment |
add a comment |
When you're using Number in filter, Actually it is passing each item of Array to Number constructor and in case of string or 0 Number will return NaN or 0 and both of them are false so filter is filtering out both of them
whereas when you're using typeof then 0 has "number" type so it is returning true and filter method doesn't filtering it out
answered 1 hour ago
Abhay Sehgal
16318
1
This answer with @adiga falsy explanation solves my confusing :)
– imckl
1 hour ago
add a comment |
When you're using Number in filter, Actually it is passing each item of Array to Number constructor and in case of string or 0 Number will return NaN or 0 and both of them are false so filter is filtering out both of them
whereas when you're using typeof then 0 has "number" type so it is returning true and filter method doesn't filtering it out
answered 1 hour ago
Abhay Sehgal
16318
1
This answer with @adiga falsy explanation solves my confusing :)
– imckl
1 hour ago
add a comment |
When you're using Number in filter, Actually it is passing each item of Array to Number constructor and in case of string or 0 Number will return NaN or 0 and both of them are false so filter is filtering out both of them
whereas when you're using typeof then 0 has "number" type so it is returning true and filter method doesn't filtering it out
answered 1 hour ago
Abhay Sehgal
16318
When you're using Number in filter, Actually it is passing each item of Array to Number constructor and in case of string or 0 Number will return NaN or 0 and both of them are false so filter is filtering out both of them
whereas when you're using typeof then 0 has "number" type so it is returning true and filter method doesn't filtering it out
answered 1 hour ago
Abhay Sehgal
16318
answered 1 hour ago
Abhay Sehgal
16318
answered 1 hour ago
Abhay Sehgal
16318
answered 1 hour ago
Abhay Sehgal
16318
16318
1
This answer with @adiga falsy explanation solves my confusing :)
– imckl
1 hour ago
add a comment |
1
This answer with @adiga falsy explanation solves my confusing :)
– imckl
1 hour ago
1
1
This answer with @adiga falsy explanation solves my confusing :)
– imckl
1 hour ago
This answer with @adiga falsy explanation solves my confusing :)
– imckl
1 hour ago
add a comment |
It's because 0 is a falsy value which returns false
Documentation
https://developer.mozilla.org/en-US/docs/Glossary/Falsy
answered 1 hour ago
AnonymousSB
2,149220
add a comment |
It's because 0 is a falsy value which returns false
Documentation
https://developer.mozilla.org/en-US/docs/Glossary/Falsy
answered 1 hour ago
AnonymousSB
2,149220
add a comment |
It's because 0 is a falsy value which returns false
Documentation
https://developer.mozilla.org/en-US/docs/Glossary/Falsy
answered 1 hour ago
AnonymousSB
2,149220
It's because 0 is a falsy value which returns false
Documentation
https://developer.mozilla.org/en-US/docs/Glossary/Falsy
answered 1 hour ago
AnonymousSB
2,149220
edited 1 hour ago
answered 1 hour ago
AnonymousSB
2,149220
answered 1 hour ago
AnonymousSB
2,149220
answered 1 hour ago
AnonymousSB
2,149220
2,149220
add a comment |
add a comment |
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