W3CSchools has this example:
var fruits = ["Banana", "Orange", "Apple", "Mango"];
fruits.sort();
fruits.reverse();
Is this the most efficient way to sort strings in descending order in Javascript?
One of the answers is using localeCompare. Just curious whether if we do reverse(), will that work for all locales (Maybe this is a separate question - Just let me know in the comments)?
If you consider
obj.sort().reverse();
VS
obj.sort((a, b) => (a > b ? -1 : 1))
VS
obj.sort((a, b) => b.localeCompare(a) )
The performance winner is : obj.sort().reverse().
Testing with an array of 10.000 elements,
obj.sort().reverse()is faster thanobj.sort( function )(except on chrome), andobj.sort( function )(usinglocalCompare).
Performance test here :
var results = [[],[],[]]
for(let i = 0; i < 100; i++){
const randomArrayGen = () => Array.from({length: 10000}, () => Math.random().toString(30));
const randomArray = randomArrayGen();
const copyArray = x => x.slice();
obj = copyArray(randomArray);
let t0 = performance.now();
obj.sort().reverse();
let t1 = performance.now();
obj = copyArray(randomArray);
let t2 = performance.now();
obj.sort((a, b) => (a > b ? -1 : 1))
let t3 = performance.now();
obj = copyArray(randomArray);
let t4 = performance.now();
obj.sort((a, b) => b.localeCompare(a))
let t5 = performance.now();
results[0].push(t1 - t0);
results[1].push(t3 - t2);
results[2].push(t5 - t4);
}
const calculateAverage = x => x.reduce((a,b) => a + b) / x.length ;
console.log("obj.sort().reverse(): " + calculateAverage(results[0]));
console.log("obj.sort((a, b) => (a > b ? -1 : 1)): " + calculateAverage(results[1]));
console.log("obj.sort((a, b) => b.localeCompare(a)): " + calculateAverage(results[2]));Using just sort and reverse a > Z , that is wrong if you want to order lower cases and upper cases strings:
var arr = ["a","b","c","A","B","Z"];
arr.sort().reverse();
console.log(arr)//<-- [ 'c', 'b', 'a', 'Z', 'B', 'A' ] wrong!!!English characters
var arr = ["a","b","c","A","B","Z"];
arr.sort((a,b)=>b.localeCompare(a))
console.log(arr)Special characters using locales, in this example es (spanish)
var arr = ["a", "á", "b","c","A","Á","B","Z"];
arr.sort((a, b) => b.localeCompare(a, 'es', {sensitivity: 'base'}))
console.log(arr)sensitivity in this case is base:
Only strings that differ in base letters compare as unequal. Examples: a ≠ b, a = á, a = A.
The easiest way to revers the order of sorting is by swapping the operands. In ES2015 that's as easy as [b, a] = [a, b]. A full example:
function compareWithOrder(a, b, shouldReverse = false) {
if (shouldReverse) {
[b, a] = [a, b]
}
return yourComparatorFn(a, b)
}