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Course Introduction：To check whether a certain property exists in a JavaScript object, there are three main methods: 1. Use the in operator to check the properties in the object and its prototype chain; 2. Use the hasOwnProperty() method to check only the properties of the object itself; 3. Use Object.hasOwn() as an alternative to hasOwnProperty in modern environments. These three methods have their own applicable scenarios. In is suitable for checking that contains inherited properties, while hasOwnProperty and Object.hasOwn() are used to exclude inherited properties and only check the object itself. The Object.hasOwn() syntax is clearer and less prone to errors, but has poor compatibility.

2025-07-02 comment 0  764

Course Introduction：In JavaScript, you can use the in operator, hasOwnProperty method or Object.keys() to match include(). 1. Use the in operator to check the keys on the object itself and the prototype chain, which is suitable for situations where the key source is uncertain; 2. Use the hasOwnProperty() method (or the safer Object.prototype.hasOwnProperty.call(obj,key)) to only check the properties of the object itself to avoid interference from the prototype chain; 3. Use Object.keys(obj).includes(key) to judge with the help of an array method.

2025-07-18 comment 0  552

Course Introduction：Use Object.hasOwn() to check whether the object has its own properties. It is a modern security alternative to hasOwnProperty(), which can avoid errors when hasOwnProperty is overwritten; 2. Use the in operator to check whether the property exists, including inherited properties; 3. Avoid judging whether the property exists by comparing undefined, because the property may indeed exist but the value is undefined; therefore, in modern JavaScript, it is recommended to use Object.hasOwn(obj,'prop') to check the own properties first. If you need to include inherited properties, use 'prop'inobj.

2025-07-28 comment 0  178

Course Introduction：This article presents a solution for iterating through nested objects recursively in JavaScript. It utilizes the for...in loop and handles inherited properties using the hasOwnProperty method. A recursive function is employed to perform the iteration

2024-10-22 comment 0  382

Course Introduction：The following methods can be used to determine whether the object properties exist: 1. Use the in operator to check whether the properties exist in the object or prototype chain; 2. Use hasOwnProperty() or Object.prototype.hasOwnProperty.call(obj,'prop') to check the object's own properties; 3. Use !==undefined to determine whether the properties have valid values; 4. Get all property names through Object.keys() or Reflect.ownKeys(). These methods are applicable to different scenarios. If you need to determine whether the attribute really exists, it is recommended to use in or hasOwnProperty. If you need to confirm that the attribute value is valid and available!

2025-08-07 comment 0  485

Course Elementary  13826

Course Introduction：Scala Tutorial Scala is a multi-paradigm programming language, designed to integrate various features of object-oriented programming and functional programming.

Course Elementary  82370

Course Introduction："CSS Online Manual" is the official CSS online reference manual. This CSS online development manual contains various CSS properties, definitions, usage methods, example operations, etc. It is an indispensable online query manual for WEB programming learners and developers! CSS: Cascading Style Sheets (English full name: Cascading Style Sheets) is an application used to express HTML (Standard Universal Markup Language).

Course Elementary  13187

Course Introduction：SVG is a markup language for vector graphics in HTML5. It maintains powerful drawing capabilities and at the same time has a very high-end interface to operate graphics by directly operating Dom nodes. This "SVG Tutorial" is intended to allow students to master the SVG language and some of its corresponding APIs, combined with the knowledge of 2D drawing, so that students can render and control complex graphics on the page.

Course Elementary  24635

Course Introduction：In the "AngularJS Chinese Reference Manual", AngularJS extends HTML with new attributes and expressions. AngularJS can build a single page application (SPAs: Single Page Applications). AngularJS is very easy to learn.

Course Elementary  27494

Course Introduction：Go is a new language, a concurrent, garbage-collected, fast-compiled language. It can compile a large Go program in a few seconds on a single computer. Go provides a model for software construction that makes dependency analysis easier and avoids most C-style include files and library headers. Go is a statically typed language, and its type system has no hierarchy. Therefore users do not need to spend time defining relationships between types, which feels more lightweight than typical object-oriented languages. Go is a completely garbage-collected language and provides basic support for concurrent execution and communication. By its design, Go is intended to provide a method for constructing system software on multi-core machines.