Sorting strings in descending order in Javascript (Most efficiently)?

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)
}

If you consider

obj.sort().reverse();

obj.sort((a, b) => (a > b ? -1 : 1))

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 than obj.sort( function ) (except on chrome), and obj.sort( function ) (using localCompare).

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.

Sorting strings in descending order in Javascript (Most efficiently)?

Tags:

Javascript

Sorting

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