An **`array.sort()` function** is used to sort an array in JavaScript. By default, it sorts the array in ascending order.

# Syntax
`array.sort()` is called on the array we want to sort. However, by default, it considers the elements of the array as strings; "100" is lower than "50" because "1" comes before "5". 

To avoid this, an *optional* argument, which is a user-defined `compare function`, can be passed to this function.

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## compareFunction(a, b)
In case we pass this optional parameter, the `sort()` method takes the value at index 0 as `a` and every other value one by one as `b` to pass on to this compare function. Sorting is then done based on its return value:
1. **return value < 0 :** `a` is placed before `b`.
2. **return value > 0 :** `a` is placed after `b`.
3. **return value = 0 :** Keeps the same order as in the original array.

# Example

The example below shows a numeric array sorted with and without a compare function:

var numbers = [50, 100, 2, 0];

// Without compare function
console.log("Without compare function:");
numbers.sort();
console.log(numbers);

// With a compare function
console.log("With a compare function:");
numbers.sort(function(a, b){
    return a - b;
});
console.log(numbers);

JavaScript array.sort() method

JavaScript's array.sort() sorts arrays in ascending order, treating elements as strings unless a compare function is provided.

JavaScript array.sort() method

Syntax

compareFunction(a, b)

How the compare function works:

Example