How to pass a custom sort function in js and how does it work?
js
var numbers = [4, 2, 5, 1, 3];
numbers.sort(function (a, b) {
return a - b;
});
console.log(numbers);
// [1, 2, 3, 4, 5]
function compare(a, b) {
if (a is less than b by some ordering criterion) {
return -1;
}
if (a is greater than b by the ordering criterion) {
return 1;
}
// a must be equal to b
return 0;
}
This is how the compare function works
If compareFunction
is supplied, all non-undefined
array elements are sorted according to the return value of the compare function (all undefined
elements are sorted to the end of the array, with no call to compareFunction
). If a
and b
are two elements being compared, then:
- If
compareFunction(a, b)
returns less than 0, sorta
to an index lower thanb
(i.e.a
comes first). - If
compareFunction(a, b)
returns 0, leavea
andb
unchanged with respect to each other, but sorted with respect to all different elements. Note: the ECMAscript standard does not guarantee this behavior, thus, not all browsers (e.g. Mozilla versions dating back to at least 2003) respect this. - If
compareFunction(a, b)
returns greater than 0, sortb
to an index lower thana
(i.e.b
comes first). compareFunction(a, b)
must always return the same value when given a specific pair of elementsa
andb
as its two arguments. If inconsistent results are returned, then the sort order is undefined.
Resources
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/sort