Explore what built-in objects are in js

Explore the built-in objects in JavaScript

JavaScript is a high-level, interpreted programming language that is widely used in web development, mobile applications, and back-end development. field. In JavaScript, there are many built-in objects that help us perform various operations and processing. This article will explore some common JavaScript built-in objects and provide specific code examples.

1. Array (array) object
   The Array object is one of the most frequently used built-in objects in JavaScript and is used to store and manipulate a set of values. The following is sample code for some commonly used array object methods:

// 创建一个空数组
let myArray = [];

// 添加元素到数组末尾
myArray.push("apple");
myArray.push("banana");
myArray.push("orange");

// 获取数组长度
console.log(myArray.length); // 输出：3

// 访问数组中的元素
console.log(myArray[0]); // 输出：apple

// 遍历数组元素
myArray.forEach(function(element) {
    console.log(element);
});

// 判断元素是否存在于数组中
console.log(myArray.includes("apple")); // 输出：true

// 删除数组中的元素
myArray.splice(1, 1); // 从索引为1的位置删除一个元素

// 拷贝数组
let newArray = myArray.slice();

2. Math (math) object
   The Math object provides a series of mathematics-related methods and properties. The following is sample code for some commonly used Math object methods:

// 计算平方根
console.log(Math.sqrt(16)); // 输出：4

// 计算绝对值
console.log(Math.abs(-10)); // 输出：10

// 计算最大值和最小值
console.log(Math.max(5, 8, 3)); // 输出：8
console.log(Math.min(5, 8, 3)); // 输出：3

// 生成随机数
console.log(Math.random()); // 输出：0到1之间的随机数

// 向上取整和向下取整
console.log(Math.ceil(3.6)); // 输出：4
console.log(Math.floor(3.6)); // 输出：3

3. Date (date) object
   The Date object is used to process dates and times. The following is sample code for some commonly used Date object methods:

// 获取当前日期和时间
let currentDate = new Date();
console.log(currentDate); // 输出：当前日期和时间的字符串表示

// 获取年、月、日等信息
console.log(currentDate.getFullYear()); // 输出：当前年份
console.log(currentDate.getMonth()); // 输出：当前月份（0-11）
console.log(currentDate.getDate()); // 输出：当前日期（1-31）
console.log(currentDate.getHours()); // 输出：当前小时（0-23）
console.log(currentDate.getMinutes()); // 输出：当前分钟（0-59）
console.log(currentDate.getSeconds()); // 输出：当前秒数（0-59）

// 获取两个日期之间的时间间隔
let pastDate = new Date('2022-01-01');
let timeDiff = currentDate - pastDate;
console.log(timeDiff); // 输出：时间间隔的毫秒数

4. String (string) object
   String object is used to process strings. Here is sample code for some commonly used String object methods:

// 获取字符串长度
let myString = "Hello, World!";
console.log(myString.length); // 输出：13

// 截取字符串
console.log(myString.slice(0, 5)); // 输出：Hello

// 查找子字符串的位置
console.log(myString.indexOf("World")); // 输出：7

// 替换字符串
console.log(myString.replace("World", "JavaScript")); // 输出：Hello, JavaScript

// 分割字符串为数组
console.log(myString.split(",")); // 输出：['Hello', ' World!']

These are just some examples of built-in objects and methods in JavaScript, there are many other built-in objects to explore and use. Understanding and skillfully using these built-in objects can greatly improve the efficiency and flexibility of JavaScript programming. I hope this article will help you learn about JavaScript's built-in objects.

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