`Sort`

Imagine a million lines of text—with no sorting it is impossible to find a certain line. But with sorting it can be easily located.

In Node.js we discover a sort method on arrays. This method can receive a function that determines how elements are sorted. With no arguments, it sorts in an ascending order.

First example

Here we introduce an array called "patterns" that has 3 strings in it. We then invoke sort() on our patterns array.

Result The array's elements are reordered. The string "abc" comes first as it is the earliest alphabetically.

var patterns = ["def", "xyz", "abc"];
// Sort the string array.
patterns.sort();
console.log("SORTED: " + patterns);
SORTED: abc,def,xyz

Modifies in-place

We can assign a variable to the result of sort() but there is no point to this. Sort() modifies the existing array.

Tip To keep the originally-ordered array around, a copy of the array would need to be made.

var patterns = ["def", "xyz", "abc"];
var result = patterns.sort();

// The original array is sorted.
console.log("VARIABLE 1: " + patterns);
console.log("VARIABLE 2: " + result);VARIABLE 1: abc,def,xyz
VARIABLE 2: abc,def,xyz

Integer array

In most programming languages numbers are sorted as numbers. But in JavaScript we find that numbers are sorted as strings. So 10 comes before 2 because 1 comes before 2.

Here We override the default sorting behavior with a function. In our function "compare" we sort two integers by their difference.

So Numbers are sorted by their numeric values, and smaller numbers precede larger ones.

var numbers = [-1, 100, 10, 1, 2, 3];

// Numbers are sorted as strings by default.
numbers.sort();
console.log("SORT 1: " + numbers);

// This function sorts numbers.
// ... We compare two numbers by subtracting one from the other.
var compare = function(a, b) {
    return a - b;
};

// Sort numbers in a numeric way.
numbers.sort(compare);
console.log("SORT 2: " + numbers);SORT 1: -1,1,10,100,2,3
SORT 2: -1,1,2,3,10,100

`LocaleCompare`

The localeCompare method handles non-ASCII characters (like those with accents) in a correct way. It should be used when sorting strings.

Here We use localCompare to sort a string array from low to high (in ascending alphabetical order).

Then We use a descending string sort. We compare the second string to the first in reverseAlphabetical.

Tip It is possible to call reverse() after sorting a string array. But with localeCompare we can directly sort in reverse order.

var unsorted = ["def", "xyz", "ghi", "abc"];

function alphabetical(a, b) {
    // Use localeCompare.
    return a.localeCompare(b);
}

function reverseAlphabetical(a, b) {
    // Use localeCompare with second compared to first.
    return b.localeCompare(a);
}

// Sort in alphabetical order.
unsorted.sort(alphabetical);
console.log("LOCALECOMPARE 1: " + unsorted);

// Sort in reverse alphabetical order.
unsorted.sort(reverseAlphabetical);
console.log("LOCALECOMPARE 2: " + unsorted);LOCALECOMPARE 1: abc,def,ghi,xyz
LOCALECOMPARE 2: xyz,ghi,def,abc

Arrays are common in Node programs—we use them everywhere. With sort() we change the ordering of elements in arrays to conform to a pattern.