Different output calling javascript sort function twice
2
I'm facing with a sorting problem in javascript. I wrote a simple sorting function where I want the null elements on top:
This is the function:
var mySort = function(a, b) {
if (!a && !b) return 0;
if (!a) return -1;
if (!b) return -1;
if (a > b) return 1;
if (a < b) return -1;
return 0;
}
Let's take the following array as example:
var array = [1, 9, 4, 8, null, 2, 3, 4, null, 6, 3, 2, 8, 9, 5];
By calling array.sort(mySort) the non null values are always sorted, but the null values position alternate from the beginning and the end of the array:
Odd calls: [null, null, 1, 2, 2, 3, 3, 4, 4, 5, 6, 8, 8, 9, 9]
Even calls: [1, 2, 2, 3, 3, 4, 4, 5, 6, 8, 8, 9, 9, null, null]
Why?
Edit:
In a comment HMR head me to an error in the algorithm: if (!b) return -1; should be if (!b) return 1;. Now it works fine with stings and numbers.
javascript sorting null
asked Nov 21 '18 at 15:53
EmaborsaEmaborsa
95331133
|
show 1 more comment
2
I'm facing with a sorting problem in javascript. I wrote a simple sorting function where I want the null elements on top:
This is the function:
var mySort = function(a, b) {
if (!a && !b) return 0;
if (!a) return -1;
if (!b) return -1;
if (a > b) return 1;
if (a < b) return -1;
return 0;
}
Let's take the following array as example:
var array = [1, 9, 4, 8, null, 2, 3, 4, null, 6, 3, 2, 8, 9, 5];
By calling array.sort(mySort) the non null values are always sorted, but the null values position alternate from the beginning and the end of the array:
Odd calls: [null, null, 1, 2, 2, 3, 3, 4, 4, 5, 6, 8, 8, 9, 9]
Even calls: [1, 2, 2, 3, 3, 4, 4, 5, 6, 8, 8, 9, 9, null, null]
Why?
Edit:
In a comment HMR head me to an error in the algorithm: if (!b) return -1; should be if (!b) return 1;. Now it works fine with stings and numbers.
javascript sorting null
asked Nov 21 '18 at 15:53
EmaborsaEmaborsa
95331133
2
You can call it as many times as you want if you do:array.slice().sort(mySort)if one item is falsy (null) it's either put on the start or the end but if they're both null then none of the items are moved. So the nulls will group at the start or the end. If you doif (!b) return 1;then it'll also always be the same.
– HMR
Nov 21 '18 at 16:02
I don't really get the point of your answer. I already know about slicing the array, but IMHO it is a hack. I'd like to know why the null are switched even if the function is the same...it should be always the same result...
– Emaborsa
Nov 22 '18 at 7:00
No it doesn't. sort mutates and you return -1 for cases where a is null and b is not or vice versa, this causes null's to either be at the start or at the end depending on the order sort will compare the items and where the items were to start with. You could either not mutate the array (useslice) or return a different value when one is null.
– HMR
Nov 22 '18 at 8:03
2
Damn....if (!b) return -1;is wrong, it should beif (!b) return 1;Now it works fine!.Thanks!
– Emaborsa
Nov 22 '18 at 8:05
do you havenullor'null'as string in the array?
– Nina Scholz
Nov 22 '18 at 10:16
|
show 1 more comment
2
2
2
I'm facing with a sorting problem in javascript. I wrote a simple sorting function where I want the null elements on top:
This is the function:
var mySort = function(a, b) {
if (!a && !b) return 0;
if (!a) return -1;
if (!b) return -1;
if (a > b) return 1;
if (a < b) return -1;
return 0;
}
Let's take the following array as example:
var array = [1, 9, 4, 8, null, 2, 3, 4, null, 6, 3, 2, 8, 9, 5];
By calling array.sort(mySort) the non null values are always sorted, but the null values position alternate from the beginning and the end of the array:
Odd calls: [null, null, 1, 2, 2, 3, 3, 4, 4, 5, 6, 8, 8, 9, 9]
Even calls: [1, 2, 2, 3, 3, 4, 4, 5, 6, 8, 8, 9, 9, null, null]
Why?
Edit:
In a comment HMR head me to an error in the algorithm: if (!b) return -1; should be if (!b) return 1;. Now it works fine with stings and numbers.
javascript sorting null
asked Nov 21 '18 at 15:53
EmaborsaEmaborsa
95331133
I'm facing with a sorting problem in javascript. I wrote a simple sorting function where I want the null elements on top:
This is the function:
var mySort = function(a, b) {
if (!a && !b) return 0;
if (!a) return -1;
if (!b) return -1;
if (a > b) return 1;
if (a < b) return -1;
return 0;
}
Let's take the following array as example:
var array = [1, 9, 4, 8, null, 2, 3, 4, null, 6, 3, 2, 8, 9, 5];
By calling array.sort(mySort) the non null values are always sorted, but the null values position alternate from the beginning and the end of the array:
Odd calls: [null, null, 1, 2, 2, 3, 3, 4, 4, 5, 6, 8, 8, 9, 9]
Even calls: [1, 2, 2, 3, 3, 4, 4, 5, 6, 8, 8, 9, 9, null, null]
Why?
Edit:
In a comment HMR head me to an error in the algorithm: if (!b) return -1; should be if (!b) return 1;. Now it works fine with stings and numbers.
javascript sorting null
javascript sorting null
asked Nov 21 '18 at 15:53
EmaborsaEmaborsa
95331133
asked Nov 21 '18 at 15:53
EmaborsaEmaborsa
95331133
edited Nov 22 '18 at 8:40
Emaborsa
asked Nov 21 '18 at 15:53
EmaborsaEmaborsa
95331133
asked Nov 21 '18 at 15:53
EmaborsaEmaborsa
95331133
asked Nov 21 '18 at 15:53
EmaborsaEmaborsa
95331133
95331133
2
You can call it as many times as you want if you do:array.slice().sort(mySort)if one item is falsy (null) it's either put on the start or the end but if they're both null then none of the items are moved. So the nulls will group at the start or the end. If you doif (!b) return 1;then it'll also always be the same.
– HMR
Nov 21 '18 at 16:02
I don't really get the point of your answer. I already know about slicing the array, but IMHO it is a hack. I'd like to know why the null are switched even if the function is the same...it should be always the same result...
– Emaborsa
Nov 22 '18 at 7:00
No it doesn't. sort mutates and you return -1 for cases where a is null and b is not or vice versa, this causes null's to either be at the start or at the end depending on the order sort will compare the items and where the items were to start with. You could either not mutate the array (useslice) or return a different value when one is null.
– HMR
Nov 22 '18 at 8:03
2
Damn....if (!b) return -1;is wrong, it should beif (!b) return 1;Now it works fine!.Thanks!
– Emaborsa
Nov 22 '18 at 8:05
do you havenullor'null'as string in the array?
– Nina Scholz
Nov 22 '18 at 10:16
|
show 1 more comment
2
You can call it as many times as you want if you do:array.slice().sort(mySort)if one item is falsy (null) it's either put on the start or the end but if they're both null then none of the items are moved. So the nulls will group at the start or the end. If you doif (!b) return 1;then it'll also always be the same.
– HMR
Nov 21 '18 at 16:02
I don't really get the point of your answer. I already know about slicing the array, but IMHO it is a hack. I'd like to know why the null are switched even if the function is the same...it should be always the same result...
– Emaborsa
Nov 22 '18 at 7:00
No it doesn't. sort mutates and you return -1 for cases where a is null and b is not or vice versa, this causes null's to either be at the start or at the end depending on the order sort will compare the items and where the items were to start with. You could either not mutate the array (useslice) or return a different value when one is null.
– HMR
Nov 22 '18 at 8:03
2
Damn....if (!b) return -1;is wrong, it should beif (!b) return 1;Now it works fine!.Thanks!
– Emaborsa
Nov 22 '18 at 8:05
do you havenullor'null'as string in the array?
– Nina Scholz
Nov 22 '18 at 10:16
2
2
You can call it as many times as you want if you do:
array.slice().sort(mySort) if one item is falsy (null) it's either put on the start or the end but if they're both null then none of the items are moved. So the nulls will group at the start or the end. If you do if (!b) return 1; then it'll also always be the same.– HMR
Nov 21 '18 at 16:02
You can call it as many times as you want if you do:
array.slice().sort(mySort) if one item is falsy (null) it's either put on the start or the end but if they're both null then none of the items are moved. So the nulls will group at the start or the end. If you do if (!b) return 1; then it'll also always be the same.– HMR
Nov 21 '18 at 16:02
I don't really get the point of your answer. I already know about slicing the array, but IMHO it is a hack. I'd like to know why the null are switched even if the function is the same...it should be always the same result...
– Emaborsa
Nov 22 '18 at 7:00
I don't really get the point of your answer. I already know about slicing the array, but IMHO it is a hack. I'd like to know why the null are switched even if the function is the same...it should be always the same result...
– Emaborsa
Nov 22 '18 at 7:00
No it doesn't. sort mutates and you return -1 for cases where a is null and b is not or vice versa, this causes null's to either be at the start or at the end depending on the order sort will compare the items and where the items were to start with. You could either not mutate the array (use
slice) or return a different value when one is null.– HMR
Nov 22 '18 at 8:03
No it doesn't. sort mutates and you return -1 for cases where a is null and b is not or vice versa, this causes null's to either be at the start or at the end depending on the order sort will compare the items and where the items were to start with. You could either not mutate the array (use
slice) or return a different value when one is null.– HMR
Nov 22 '18 at 8:03
2
2
Damn....
if (!b) return -1; is wrong, it should be if (!b) return 1; Now it works fine!.Thanks!– Emaborsa
Nov 22 '18 at 8:05
Damn....
if (!b) return -1; is wrong, it should be if (!b) return 1; Now it works fine!.Thanks!– Emaborsa
Nov 22 '18 at 8:05
do you have
null or 'null' as string in the array?– Nina Scholz
Nov 22 '18 at 10:16
do you have
null or 'null' as string in the array?– Nina Scholz
Nov 22 '18 at 10:16
|
show 1 more comment
1 Answer
1
active
oldest
votes
1
You need to use the relation between two items. If both items are null, then change nothing, if you have one null value, then it depends on the position.
The best way is to check the items and get the delta of the check for sorting.
function mySort(a, b) {
return (b === null) - (a === null) || a - b;
}
var array = [1, 9, 4, 8, null, 2, 3, 4, null, 6, 3, 2, 8, 9, 5];
array.sort(mySort);
console.log(array);
array.sort(mySort);
console.log(array);.as-console-wrapper { max-height: 100% !important; top: 0; }answered Nov 21 '18 at 16:02
Nina ScholzNina Scholz
178k1491159
I copied your example, it behavies as mine does. Try to call the sort a second time, the null values will go at the end.
– Emaborsa
Nov 22 '18 at 6:58
it keeps the order. on which user agent is this running?
– Nina Scholz
Nov 22 '18 at 7:04
Chrome Version 70.0.3538.102
– Emaborsa
Nov 22 '18 at 7:07
it is working fine with 70.0.3538.102 and the very actual version 70.0.3538.110 on windows.
– Nina Scholz
Nov 22 '18 at 7:09
Ok, but I need something that works on (almost) every browser.
– Emaborsa
Nov 22 '18 at 7:11
|
show 1 more comment
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1 Answer
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1
You need to use the relation between two items. If both items are null, then change nothing, if you have one null value, then it depends on the position.
The best way is to check the items and get the delta of the check for sorting.
function mySort(a, b) {
return (b === null) - (a === null) || a - b;
}
var array = [1, 9, 4, 8, null, 2, 3, 4, null, 6, 3, 2, 8, 9, 5];
array.sort(mySort);
console.log(array);
array.sort(mySort);
console.log(array);.as-console-wrapper { max-height: 100% !important; top: 0; }answered Nov 21 '18 at 16:02
Nina ScholzNina Scholz
178k1491159
I copied your example, it behavies as mine does. Try to call the sort a second time, the null values will go at the end.
– Emaborsa
Nov 22 '18 at 6:58
it keeps the order. on which user agent is this running?
– Nina Scholz
Nov 22 '18 at 7:04
Chrome Version 70.0.3538.102
– Emaborsa
Nov 22 '18 at 7:07
it is working fine with 70.0.3538.102 and the very actual version 70.0.3538.110 on windows.
– Nina Scholz
Nov 22 '18 at 7:09
Ok, but I need something that works on (almost) every browser.
– Emaborsa
Nov 22 '18 at 7:11
|
show 1 more comment
1
You need to use the relation between two items. If both items are null, then change nothing, if you have one null value, then it depends on the position.
The best way is to check the items and get the delta of the check for sorting.
function mySort(a, b) {
return (b === null) - (a === null) || a - b;
}
var array = [1, 9, 4, 8, null, 2, 3, 4, null, 6, 3, 2, 8, 9, 5];
array.sort(mySort);
console.log(array);
array.sort(mySort);
console.log(array);.as-console-wrapper { max-height: 100% !important; top: 0; }answered Nov 21 '18 at 16:02
Nina ScholzNina Scholz
178k1491159
I copied your example, it behavies as mine does. Try to call the sort a second time, the null values will go at the end.
– Emaborsa
Nov 22 '18 at 6:58
it keeps the order. on which user agent is this running?
– Nina Scholz
Nov 22 '18 at 7:04
Chrome Version 70.0.3538.102
– Emaborsa
Nov 22 '18 at 7:07
it is working fine with 70.0.3538.102 and the very actual version 70.0.3538.110 on windows.
– Nina Scholz
Nov 22 '18 at 7:09
Ok, but I need something that works on (almost) every browser.
– Emaborsa
Nov 22 '18 at 7:11
|
show 1 more comment
1
1
1
You need to use the relation between two items. If both items are null, then change nothing, if you have one null value, then it depends on the position.
The best way is to check the items and get the delta of the check for sorting.
function mySort(a, b) {
return (b === null) - (a === null) || a - b;
}
var array = [1, 9, 4, 8, null, 2, 3, 4, null, 6, 3, 2, 8, 9, 5];
array.sort(mySort);
console.log(array);
array.sort(mySort);
console.log(array);.as-console-wrapper { max-height: 100% !important; top: 0; }answered Nov 21 '18 at 16:02
Nina ScholzNina Scholz
178k1491159
You need to use the relation between two items. If both items are null, then change nothing, if you have one null value, then it depends on the position.
The best way is to check the items and get the delta of the check for sorting.
function mySort(a, b) {
return (b === null) - (a === null) || a - b;
}
var array = [1, 9, 4, 8, null, 2, 3, 4, null, 6, 3, 2, 8, 9, 5];
array.sort(mySort);
console.log(array);
array.sort(mySort);
console.log(array);.as-console-wrapper { max-height: 100% !important; top: 0; }function mySort(a, b) {
return (b === null) - (a === null) || a - b;
}
var array = [1, 9, 4, 8, null, 2, 3, 4, null, 6, 3, 2, 8, 9, 5];
array.sort(mySort);
console.log(array);
array.sort(mySort);
console.log(array);.as-console-wrapper { max-height: 100% !important; top: 0; }function mySort(a, b) {
return (b === null) - (a === null) || a - b;
}
var array = [1, 9, 4, 8, null, 2, 3, 4, null, 6, 3, 2, 8, 9, 5];
array.sort(mySort);
console.log(array);
array.sort(mySort);
console.log(array);.as-console-wrapper { max-height: 100% !important; top: 0; }answered Nov 21 '18 at 16:02
Nina ScholzNina Scholz
178k1491159
edited Nov 22 '18 at 7:04
answered Nov 21 '18 at 16:02
Nina ScholzNina Scholz
178k1491159
answered Nov 21 '18 at 16:02
Nina ScholzNina Scholz
178k1491159
answered Nov 21 '18 at 16:02
Nina ScholzNina Scholz
178k1491159
178k1491159
I copied your example, it behavies as mine does. Try to call the sort a second time, the null values will go at the end.
– Emaborsa
Nov 22 '18 at 6:58
it keeps the order. on which user agent is this running?
– Nina Scholz
Nov 22 '18 at 7:04
Chrome Version 70.0.3538.102
– Emaborsa
Nov 22 '18 at 7:07
it is working fine with 70.0.3538.102 and the very actual version 70.0.3538.110 on windows.
– Nina Scholz
Nov 22 '18 at 7:09
Ok, but I need something that works on (almost) every browser.
– Emaborsa
Nov 22 '18 at 7:11
|
show 1 more comment
I copied your example, it behavies as mine does. Try to call the sort a second time, the null values will go at the end.
– Emaborsa
Nov 22 '18 at 6:58
it keeps the order. on which user agent is this running?
– Nina Scholz
Nov 22 '18 at 7:04
Chrome Version 70.0.3538.102
– Emaborsa
Nov 22 '18 at 7:07
it is working fine with 70.0.3538.102 and the very actual version 70.0.3538.110 on windows.
– Nina Scholz
Nov 22 '18 at 7:09
Ok, but I need something that works on (almost) every browser.
– Emaborsa
Nov 22 '18 at 7:11
I copied your example, it behavies as mine does. Try to call the sort a second time, the null values will go at the end.
– Emaborsa
Nov 22 '18 at 6:58
I copied your example, it behavies as mine does. Try to call the sort a second time, the null values will go at the end.
– Emaborsa
Nov 22 '18 at 6:58
it keeps the order. on which user agent is this running?
– Nina Scholz
Nov 22 '18 at 7:04
it keeps the order. on which user agent is this running?
– Nina Scholz
Nov 22 '18 at 7:04
Chrome Version 70.0.3538.102
– Emaborsa
Nov 22 '18 at 7:07
Chrome Version 70.0.3538.102
– Emaborsa
Nov 22 '18 at 7:07
it is working fine with 70.0.3538.102 and the very actual version 70.0.3538.110 on windows.
– Nina Scholz
Nov 22 '18 at 7:09
it is working fine with 70.0.3538.102 and the very actual version 70.0.3538.110 on windows.
– Nina Scholz
Nov 22 '18 at 7:09
Ok, but I need something that works on (almost) every browser.
– Emaborsa
Nov 22 '18 at 7:11
Ok, but I need something that works on (almost) every browser.
– Emaborsa
Nov 22 '18 at 7:11
|
show 1 more comment
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2
You can call it as many times as you want if you do:
array.slice().sort(mySort)if one item is falsy (null) it's either put on the start or the end but if they're both null then none of the items are moved. So the nulls will group at the start or the end. If you doif (!b) return 1;then it'll also always be the same.– HMR
Nov 21 '18 at 16:02
I don't really get the point of your answer. I already know about slicing the array, but IMHO it is a hack. I'd like to know why the null are switched even if the function is the same...it should be always the same result...
– Emaborsa
Nov 22 '18 at 7:00
No it doesn't. sort mutates and you return -1 for cases where a is null and b is not or vice versa, this causes null's to either be at the start or at the end depending on the order sort will compare the items and where the items were to start with. You could either not mutate the array (use
slice) or return a different value when one is null.– HMR
Nov 22 '18 at 8:03
2
Damn....
if (!b) return -1;is wrong, it should beif (!b) return 1;Now it works fine!.Thanks!– Emaborsa
Nov 22 '18 at 8:05
do you have
nullor'null'as string in the array?– Nina Scholz
Nov 22 '18 at 10:16