Detailed explanation of various js built-in objects

Detailed explanation of various JS built-in objects

JavaScript is a powerful scripting language that provides many built-in objects that can help developers process data and data more efficiently. Manipulate page elements. This article will introduce several commonly used JavaScript built-in objects in detail and provide specific code examples.

1. Array (array object)

An array is an ordered collection that can store multiple values. The following are some commonly used array operation methods and properties:

• length: Returns the length of the array.
• push(): Add one or more elements to the end of the array.
• pop(): Remove and return the last element of the array.
• splice(): Add/remove elements to/from the array.
• concat(): Concatenate two or more arrays.

Code example:

let fruits = ['apple', 'banana', 'orange'];
console.log(fruits.length);  // 输出3
fruits.push('grape');
console.log(fruits);  // 输出 ['apple', 'banana', 'orange', 'grape']
fruits.pop();
console.log(fruits);  // 输出 ['apple', 'banana', 'orange']
fruits.splice(1, 1, 'kiwi');
console.log(fruits);  // 输出 ['apple', 'kiwi', 'orange']
let moreFruits = ['mango', 'pear'];
let allFruits = fruits.concat(moreFruits);
console.log(allFruits);  // 输出 ['apple', 'kiwi', 'orange', 'mango', 'pear']

2. String (String object)

A string is a sequence of characters that can be passed Object operates. The following are some commonly used string manipulation methods:

• length: Returns the length of the string.
• charAt(): Returns the character at the specified position.
• concat(): Concatenate two or more strings.
• indexOf(): Returns the first occurrence position of the specified character or string in the string.

Code example:

let str = 'Hello, World!';
console.log(str.length);  // 输出 13
console.log(str.charAt(4));  // 输出 'o'
let newStr = str.concat(' Have a nice day!');
console.log(newStr);  // 输出 'Hello, World! Have a nice day!'
console.log(str.indexOf('o'));  // 输出 4

3. Math (mathematical object)

The Math object provides many properties and methods related to mathematical calculations. The following are some commonly used Math methods:

• abs(): Returns the absolute value of a number.
• ceil(): Round a number up.
• floor(): Round a number down.
• random(): Returns a random number between 0 and 1.

Code Example:

console.log(Math.abs(-5));  // 输出 5
console.log(Math.ceil(4.3));  // 输出 5
console.log(Math.floor(4.7));  // 输出 4
console.log(Math.random());  // 输出随机数，如 0.8375921587168932

4. Date (Date Object)

Date object is used to process dates and times. The following are some commonly used Date methods:

• getDate(): Returns the number of days in the date (1-31).
• getMonth(): Returns the month (0-11) of the date.
• getFullYear(): Returns the year of the date (four digits).
• getTime(): Returns the number of milliseconds since January 1, 1970.

Code Examples:

let today = new Date();
console.log(today.getDate());  // 输出当前日期的天数
console.log(today.getMonth());  // 输出当前日期的月份
console.log(today.getFullYear());  // 输出当前日期的年份
console.log(today.getTime());  // 输出当前日期的毫秒数

These are just a few examples of JavaScript’s built-in objects, there are many other useful objects and methods available to developers. By rationally using these built-in objects, we can process data and operate pages more easily, improving development efficiency. Hope this article helps you!

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