Characteristics and usage of js built-in objects

To understand what the built-in objects are in JavaScript, you need specific code examples

JavaScript is a programming language widely used in web development. It provides a A series of built-in objects allow developers to perform various operations more conveniently. This article will introduce some commonly used JavaScript built-in objects and provide corresponding code examples to help readers understand their usage more deeply.

1. Object object
   Object is the most basic object in JavaScript, and almost all other objects inherit from it. We can use the Object object to create custom objects, and we can also use its properties and methods to operate on the object.

Example: Create an object and set properties

let person = new Object();
person.name = "张三";
person.age = 20;
person.greet = function() {
  console.log("你好，我是" + this.name + "，今年" + this.age + "岁。");
};

person.greet();  // 输出：你好，我是张三，今年20岁。

2. Array array object
   Array object is an object used to store and manipulate a set of data, which can be indexed Access and modify elements in an array. JavaScript provides many methods for operating on arrays.

Example: Create an array and loop through the elements to output it

let fruits = ["苹果", "香蕉", "橙子", "西瓜"];

for (let i = 0; i < fruits.length; i++) {
  console.log(fruits[i]);
}

// 输出：
// 苹果
// 香蕉
// 橙子
// 西瓜

3. String string object
   String object is used to represent and manipulate strings, providing many String-related methods, such as finding substrings, replacing characters, etc.

Example: Use string methods to find substrings

let str = "Hello, World!";

console.log(str.indexOf("World"));  // 输出：7
console.log(str.includes("Hello"));  // 输出：true
console.log(str.substring(7, 12));  // 输出：World
console.log(str.replace("Hello", "Hi"));  // 输出：Hi, World!

4. Math mathematical object
   The Math object provides a series of mathematics-related methods and constants, such as finding absolute values, rounding, calculating trigonometric functions, etc.

Example: Use Math object to find random numbers

let randomNum = Math.random();  // 获取0到1之间的随机数
console.log(randomNum);

let randomInt = Math.floor(Math.random() * 10);  // 获取0到9之间的随机整数
console.log(randomInt);

5. Date date object
   Date object is used to represent and operate date and time, and can obtain the current time and settings Specify time, perform operations such as adding and subtracting dates.

Example: Get the current date and time

let currentDate = new Date();  // 获取当前日期和时间
console.log(currentDate);

let year = currentDate.getFullYear();  // 获取当前年份
let month = currentDate.getMonth() + 1;  // 获取当前月份（注意：月份从0开始）
console.log(year + "-" + month);

6. RegExp regular expression object
   RegExp object is used to perform string matching and replacement operations, which can be based on patterns to search and replace strings.

Example: Use regular expressions to match and replace strings

let str = "Hello, JavaScript!";
let pattern = /JavaScript/;

console.log(pattern.test(str));  // 输出：true

let newStr = str.replace(pattern, "World");
console.log(newStr);  // 输出：Hello, World!

The above are just simple examples of some commonly used built-in objects in JavaScript. In fact, JavaScript provides more built-in objects. Create objects, including but not limited to Error, JSON, Map, Set, etc. By learning and applying these objects, developers can program JavaScript more efficiently.

The above is the detailed content of Characteristics and usage of js built-in objects. For more information, please follow other related articles on the PHP Chinese website!