Home Web Front-end JS Tutorial JS data type + reference type deep and shallow copy and memory allocation issues

JS data type + reference type deep and shallow copy and memory allocation issues

Apr 18, 2018 pm 01:59 PM
javascript Quote

This time I will bring you the data type of JS The problem of deep and shallow copying and memory allocation of reference types. What are the precautions when using JS data type reference type deep and shallow copying and memory allocation? , the following is a practical case, let’s take a look.

js deep and shallow copy problem

Shallow copy generally refers to basic type of copy

Deep copy generally refers to the copy of the reference type, and also copies the value of the reference type

Example

h5's sessionStorage can only store strings, so when you want to store json, you must use JSON.stringify() to convert json into string. Then use JSON.parse() to convert it into json data

Disadvantages: JSON.parse and JSON.stringify only support IE9 and above

To solve this problem, you can use the depth ratio copy method

Memory allocation issues in js (heap and stack)

Basic types in js are generally stored on the stack. These types each occupy a fixed size of space in the memory, and their values ​​are stored in the stack space, which we access by value.

Reference types are data of variable size, but their address size is fixed, so the address is stored on the stack and the value is stored on the heap

1. Stack memory: stores basic types. Heap memory: stores reference types (store a basic type value in the stack memory to save the address of the object in the heap memory, which is used to reference the object.)

2. The basic type is destroyed when the current execution environment ends, but the reference type will not be destroyed when the execution environment ends. This object will be recycled by the garbage collection mechanism only when all variables that reference it do not exist.

js basic data types and reference types

Basic data types include number boolean string undefined null symbol

Reference data type: array obj function

I believe you have mastered the method after reading the case in this article. For more exciting information, please pay attention to other related articles on the PHP Chinese website!

Recommended reading:



The above is the detailed content of JS data type + reference type deep and shallow copy and memory allocation issues. For more information, please follow other related articles on the PHP Chinese website!

Statement of this Website
The content of this article is voluntarily contributed by netizens, and the copyright belongs to the original author. This site does not assume corresponding legal responsibility. If you find any content suspected of plagiarism or infringement, please contact admin@php.cn

Hot AI Tools

Undresser.AI Undress

Undresser.AI Undress

AI-powered app for creating realistic nude photos

AI Clothes Remover

AI Clothes Remover

Online AI tool for removing clothes from photos.

Undress AI Tool

Undress AI Tool

Undress images for free

Clothoff.io

Clothoff.io

AI clothes remover

Video Face Swap

Video Face Swap

Swap faces in any video effortlessly with our completely free AI face swap tool!

Hot Tools

Notepad++7.3.1

Notepad++7.3.1

Easy-to-use and free code editor

SublimeText3 Chinese version

SublimeText3 Chinese version

Chinese version, very easy to use

Zend Studio 13.0.1

Zend Studio 13.0.1

Powerful PHP integrated development environment

Dreamweaver CS6

Dreamweaver CS6

Visual web development tools

SublimeText3 Mac version

SublimeText3 Mac version

God-level code editing software (SublimeText3)

How to implement an online speech recognition system using WebSocket and JavaScript How to implement an online speech recognition system using WebSocket and JavaScript Dec 17, 2023 pm 02:54 PM

How to use WebSocket and JavaScript to implement an online speech recognition system Introduction: With the continuous development of technology, speech recognition technology has become an important part of the field of artificial intelligence. The online speech recognition system based on WebSocket and JavaScript has the characteristics of low latency, real-time and cross-platform, and has become a widely used solution. This article will introduce how to use WebSocket and JavaScript to implement an online speech recognition system.

WebSocket and JavaScript: key technologies for implementing real-time monitoring systems WebSocket and JavaScript: key technologies for implementing real-time monitoring systems Dec 17, 2023 pm 05:30 PM

WebSocket and JavaScript: Key technologies for realizing real-time monitoring systems Introduction: With the rapid development of Internet technology, real-time monitoring systems have been widely used in various fields. One of the key technologies to achieve real-time monitoring is the combination of WebSocket and JavaScript. This article will introduce the application of WebSocket and JavaScript in real-time monitoring systems, give code examples, and explain their implementation principles in detail. 1. WebSocket technology

How to use JavaScript and WebSocket to implement a real-time online ordering system How to use JavaScript and WebSocket to implement a real-time online ordering system Dec 17, 2023 pm 12:09 PM

Introduction to how to use JavaScript and WebSocket to implement a real-time online ordering system: With the popularity of the Internet and the advancement of technology, more and more restaurants have begun to provide online ordering services. In order to implement a real-time online ordering system, we can use JavaScript and WebSocket technology. WebSocket is a full-duplex communication protocol based on the TCP protocol, which can realize real-time two-way communication between the client and the server. In the real-time online ordering system, when the user selects dishes and places an order

How to implement an online reservation system using WebSocket and JavaScript How to implement an online reservation system using WebSocket and JavaScript Dec 17, 2023 am 09:39 AM

How to use WebSocket and JavaScript to implement an online reservation system. In today's digital era, more and more businesses and services need to provide online reservation functions. It is crucial to implement an efficient and real-time online reservation system. This article will introduce how to use WebSocket and JavaScript to implement an online reservation system, and provide specific code examples. 1. What is WebSocket? WebSocket is a full-duplex method on a single TCP connection.

JavaScript and WebSocket: Building an efficient real-time weather forecasting system JavaScript and WebSocket: Building an efficient real-time weather forecasting system Dec 17, 2023 pm 05:13 PM

JavaScript and WebSocket: Building an efficient real-time weather forecast system Introduction: Today, the accuracy of weather forecasts is of great significance to daily life and decision-making. As technology develops, we can provide more accurate and reliable weather forecasts by obtaining weather data in real time. In this article, we will learn how to use JavaScript and WebSocket technology to build an efficient real-time weather forecast system. This article will demonstrate the implementation process through specific code examples. We

Simple JavaScript Tutorial: How to Get HTTP Status Code Simple JavaScript Tutorial: How to Get HTTP Status Code Jan 05, 2024 pm 06:08 PM

JavaScript tutorial: How to get HTTP status code, specific code examples are required. Preface: In web development, data interaction with the server is often involved. When communicating with the server, we often need to obtain the returned HTTP status code to determine whether the operation is successful, and perform corresponding processing based on different status codes. This article will teach you how to use JavaScript to obtain HTTP status codes and provide some practical code examples. Using XMLHttpRequest

What are the benefits of C++ functions returning reference types? What are the benefits of C++ functions returning reference types? Apr 20, 2024 pm 09:12 PM

The benefits of functions returning reference types in C++ include: Performance improvements: Passing by reference avoids object copying, thus saving memory and time. Direct modification: The caller can directly modify the returned reference object without reassigning it. Code simplicity: Passing by reference simplifies the code and requires no additional assignment operations.

How to use insertBefore in javascript How to use insertBefore in javascript Nov 24, 2023 am 11:56 AM

Usage: In JavaScript, the insertBefore() method is used to insert a new node in the DOM tree. This method requires two parameters: the new node to be inserted and the reference node (that is, the node where the new node will be inserted).

See all articles