how sort sorts using a-b in js code example

Example 1: javascript sort by numerical value

// Sort an array of numbers based on numerical value.
let numbers = [23, 65, 88, 12, 45, 99, 2000]

let sortednumbers = numbers.sort((a, b) => a - b);
//=> [12, 23, 45, 65, 88, 99, 2000]

Example 2: sort a string in javascript

var string='ACBacb';
var sortedString = string.split('').sort().join('');