Javascript Array Sorting Detailed _ basics

If you've been in touch with JavaScript for a while, you know the array sort function Sort,sort is a method in the array prototype, Array.prototype.sort (), sort (comparefunction), Where comparefunction is a comparison function, let's look at a description from the Mozilla MDN:
If Comparefunction is isn't supplied, elements are sorted by converting them to strings and comparing strings in LEXICOG Raphic ("dictionary" or "telephone book, ' not Numerical ' order.) For example, "80″comes before" 9″in lexicographic order, but in a numeric sort 9 comes before.

Let's look at some simple examples:

Copy Code code as follows:

Output [1, 2, 3]
Console.log ([3, 2, 1].sort ());

Output ["A", "B", "C"]
Console.log (["C", "B", "A"].sort ());

Output [1, 2, "a", "B"]
Console.log (["B", 2, "a", 1].sort ());

As you can see from the example above, the default is sorted by the order of the letters in the dictionary.

Luckily, sort accepts a custom comparison function, as in the following example:

Copy Code code as follows:

function Comparefunction (A, b) {
if (a > B) {
return-1;
}else if (a < b) {
return 1;
}else {
return 0;
}
}
Outputs ["ZUOJJ", "Benjamin", "1"]
Console.log (["Benjamin", "1", "ZUOJJ"].sort (comparefunction));

After sorting we have a question, how to control the ascending and descending?

Copy Code code as follows:

function comparefunction (flag) {
Flag = flag? Flag: "ASC";
return function (A, b) {
if (a > B) {
return flag = = "desc"? -1:1;
}else if (a < b) {
return flag = = "desc"? 1:-1;
}else {
return 0;
}
};
}
Outputs ["1", "Benjamin", "ZUOJJ"]
Console.log (["Benjamin", "1", "ZUOJJ"].sort (Comparefunction ()));
Outputs ["ZUOJJ", "Benjamin", "1"]
Console.log (["Benjamin", "1", "ZUOJJ"].sort (comparefunction ("desc"));

The collation of the comparfunction is this:
1.If it returns a negative number, a would be sorted to a lower index in the array.
2.If it returns a positive number, a would be sorted to a higher index.
3.And if it returns 0 no sorting is necessary.

Let's take a look at some of the words from the Mozilla MDN:
The behavior of the sort method changed between JavaScript 1.1 and JavaScript 1.2. To explain this description, let's look at an example:

In JavaScript 1.1, on some platforms, the sort method does not work. This is platforms for JavaScript 1.2.

In JavaScript 1.2, this is no longer converts undefined elements to null; Instead it sorts them to the "high" end of the array. Please stamp here for details.

Copy Code code as follows:

var arr = [];
Arr[0] = "Ant";
ARR[5] = "Zebra";
Outputs ["Ant", 5: "Zebra"]
Console.log (arr);
Outputs 6
Console.log (arr.length);
Outputs "Ant*****zebra"
Console.log (Arr.join ("*"));
Sort
var Sortarr = Arr.sort ();
Outputs ["Ant", "Zebra"]
Console.log (Sortarr);
Outputs 6
Console.log (sortarr.length);
Outputs "ant*zebra****"
Console.log (Sortarr.join ("*"));

I hope this article is helpful for you to learn and understand the sort () method, and it is also expected to criticize treatise in the article.

Reference Link: https://developer.mozilla.org/zh-CN/docs/Web/JavaScript/Reference/Global_Objects/Array/sort