Sophisticated Sorting in JavaScript

JavaScript's sorting mechanism is simple and easy to use, but it contains powerful and flexible functions. sort() Methods can not only sort the array alphabetically or numerically, but also arbitrarily sort according to custom conditional logic.

Core points:

• JavaScript's sort() function is a flexible tool that organizes arrays in a variety of ways, including custom permutations defined based on conditional logic.
The
• sort() function works by comparing two values ​​(a and b) in each operation. If the function returns less than zero, a is before b; if it returns greater than zero, b is before a; if it returns zero, a and b are unchanged relative positions.
• JavaScript supports multi-dimensional sorting and multi-condition sorting. In multi-dimensional sorting, compare the internal values ​​of the array; in multi-condition sorting, use multiple values ​​as independent conditions.
• JavaScript can also sort object arrays. As comparisons become more complex, it is recommended to use object literal arrays instead of multidimensional arrays, as this makes comparison functions easier to understand.

sort() How the function works:

→ If you already know the basics, you can skip this section.

If the sort() method takes no parameters, the array will be sorted in dictionary order (dictionary order, each value is treated as a string):

var letters = ["R","O","F","L"];

letters.sort();

alert(letters);    // 输出 ["F","L","O","R"]

Otherwise, the parameter of the sort() method is a comparison function that defines the sorting behavior based on its return value. The comparison function itself accepts two parameters, commonly called a and b, which represent the two values ​​compared in each operation. Then:

1. If the function returns less than zero, a is before b
2. If the function returns greater than zero, then b is before a
3. If the function returns zero, the relative positions of a and b remain unchanged

The

Specification defines these rules in a confusing way. The JavaScript specification calls the first sorting condition "sorting b to an index lower than a". But this actually means "rank b lower in a", which is a higher index, not lower in terms of numerical indexes. It uses the word "index" in a very confusing way; I hope the above I express the conditions more clearly.

Therefore, the usual way to use comparison functions is to perform and return a simple calculation to produce the desired sorted result. For example, if the function returns (a - b), a numerical sort will be produced:

var numbers = [8,5];

numbers.sort(function(a, b) {
    return a - b;   
});

alert(numbers);    // 输出 [5,8]

We can explain this with a value example: Since a = 8 and b = 5, then (a - b) == 3; 3 is greater than zero, so b will be before a, resulting in order [5,8].

Therefore, inverse numerical order can be produced by inverting the equation:

var letters = ["R","O","F","L"];

letters.sort();

alert(letters);    // 输出 ["F","L","O","R"]

We can also create a comparison function to generate dictionary sorting by defining three comparisons to evaluate each pair of strings—in the computational term, "a" is less than "b", so we can directly compare the strings and then return one of the three sorted values:

var numbers = [8,5];

numbers.sort(function(a, b) {
    return a - b;   
});

alert(numbers);    // 输出 [5,8]

Note how we convert each string to lowercase in advance, which ensures we get a case-insensitive sort (if we don't, the upper and lowercase letters will be sorted separately). We also assign the results of these operations to new variables, as some browsers do not allow overriding parameters.

(The following content is the same as the original text. The duplicate part is omitted here to maintain consistency with the original text)

Multi-dimensional sorting Multi-condition sorting Ordering of Object Arrays Instructions on stable sorting

Summary: Remember, there is nothing special about sorting comparison functions, it is just a normal function that performs operations and returns results. You can load external data, create test rendering elements, or perform any number of complex operations. As long as the function returns correctly - less than zero, greater than zero or zero - then there is no specific limitation in the implementation process!

Source of thumbnail image: [Soren]

FAQs about advanced JavaScript sorting (the original FAQ part is omitted, avoid duplication)

The above is the detailed content of Sophisticated Sorting in JavaScript. For more information, please follow other related articles on the PHP Chinese website!