Using JavaScript functions to sort and filter arrays

JavaScript function implements sorting and filtering of arrays

In JavaScript, we often need to sort and filter arrays. This article will introduce how to use JavaScript functions to sort and filter arrays, and give specific code examples.

1. Sorting arrays

JavaScript provides the sort() function for sorting arrays. The sort() function has two uses. One is to pass no parameters and sort according to the default sorting rules (sorting according to Unicode encoding); the other is to pass a custom comparison function and sort according to the return value of the function. .

For example, to sort an array containing integers, you can use the following code:

const arr = [5, 3, 8, 1, 10];

// 默认排序
const sortedArr1 = arr.sort();
console.log(sortedArr1); // [1, 10, 3, 5, 8]

// 自定义比较函数进行排序
const sortedArr2 = arr.sort((a, b) => a - b);
console.log(sortedArr2); // [1, 3, 5, 8, 10]

In the above code, by passing a comparison function (a, b) =&gt ; a - bGive the sort() function, and the elements of the array will be sorted from small to large according to the return value of the comparison function.

2. Filter arrays

JavaScript provides the filter() function for filtering arrays. The filter() function needs to pass a callback function as a parameter, and determine whether to retain the elements of the array based on the return value of the callback function.

For example, to filter an array containing integers and only retain elements greater than 5, you can use the following code:

const arr = [5, 3, 8, 1, 10];

const filteredArr = arr.filter(item => item > 5);
console.log(filteredArr); // [8, 10]

In the above code, the callback function item =&gt ; item > 5 Determine whether the element is greater than 5. Return true to retain the element, return false to filter out the element.

Comprehensive application example

The following is a comprehensive application example that demonstrates how to sort and filter an array containing objects by a certain field:

const users = [
  { name: '张三', age: 20 },
  { name: '李四', age: 25 },
  { name: '王五', age: 18 },
  { name: '赵六', age: 30 },
];

// 按年龄从小到大排序
const sortedUsers = users.sort((a, b) => a.age - b.age);
console.log(sortedUsers);

// 年龄大于20的用户
const filteredUsers = users.filter(user => user.age > 20);
console.log(filteredUsers);

In the above In the example, first sort the array containing user objects by age by passing a comparison function (a, b) => a.age - b.age, and then use the callback function user =&gt ; user.age > 20Filter out users whose age is less than or equal to 20.

Summary

This article introduces how to use JavaScript functions to sort and filter arrays. The sort() function can be used to sort the array, and the sorting rules can be customized by passing the comparison function; the filter() function can be used to filter the array based on the return value of the callback function. These array operation functions are commonly used tools in JavaScript development and provide convenient methods for processing data needs.

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