Sorting strings

Suppose we have the following array:

let names = ['Ana', 'ana', 'john', 'John']; 
console.log(names.sort()); 

What do you think would be the output? The answer is as follows:

["Ana", "John", "ana", "john"] 

Why does ana come after John when a comes first in the alphabet? The answer is because JavaScript compares each character according to its ASCII value. For example, A, J, a, and j have the decimal ASCII values of A: 65, J: 74, a: 97, and j: 106.

Therefore, J has a lower value than a, and because of this, it comes first in the alphabet.

Now, if we pass compareFunction, which contains the code to ignore the case of the letter, we will have the output ["Ana", "ana", "john", "John"], as follows:

names = ['Ana', 'ana', 'john', 'John']; // reset array original state 
console.log(names.sort((a, b) => { 
  if (a.toLowerCase() < b.toLowerCase()) { 
    return -1; 
  } 
  if (a.toLowerCase() > b.toLowerCase()) { 
    return 1; 
  } 
  return 0; 
})); 

In this case, the sort function will not have any effect; it will obey the current order of lower and uppercase letters.

If we want lowercase letters to come first in the sorted array, then we need to use the localeCompare method:

names.sort((a, b) => a.localeCompare(b)); 

The output will be ["ana", "Ana", "john", "John"].

For accented characters, we can use the localeCompare method as well:

const names2 = ['Maève', 'Maeve']; 
console.log(names2.sort((a, b) => a.localeCompare(b))); 

The output will be ["Maeve", "Maève"].