JavaScript language features do not include

As a popular programming language, JavaScript language has many features and functions. This article will explore the features of the JavaScript language and point out some of the features it does not include.

JavaScript language features:

1. Event-driven programming: The JavaScript language adopts an event-driven programming model, which means that code will be executed when an event is triggered. This programming model makes JavaScript suitable for building interactive web applications.
2. Dynamic typing: The JavaScript language is a dynamically typed language with no type declarations. This means that the type of the variable is determined at runtime, not at compile time. In this way, developers can handle data more flexibly and do not need to consider type restrictions when coding.
3. Object-oriented programming: Although the object-oriented programming model of the JavaScript language is different from traditional object-oriented programming languages, the JavaScript language does support object-oriented programming. Being object-centric, JavaScript uses the concept of prototypes to implement inheritance, making it more flexible.
4. Functional programming: The JavaScript language draws on the ideas of functional programming languages, in which functions are first-class objects. Developers can pass functions as parameters or return values, or store them in variables.
5. Weakly typed: The JavaScript language is a weakly typed language, which means that type conversion occurs at runtime. Developers need to use type conversions carefully to ensure that the code executes correctly.
6. Flexibility: The syntax and structure of the JavaScript language make it suitable for a variety of applications. It can be integrated with HTML, CSS and other web technologies, and can also be used for server-side programming.

Features not included in the JavaScript language:

1. Multi-thread support: The JavaScript language is a single-threaded language and cannot handle multiple threads. This means that JavaScript applications cannot perform multiple tasks at the same time.
2. Blocking IO: IO operations in the JavaScript language are usually non-blocking, so JavaScript applications can perform other tasks without waiting for the IO operation to complete.
3. Native file system access: Until 2019, the JavaScript language itself did not provide a native file access API, and developers usually achieved file system access by using file uploads.
4. Static type checking: The JavaScript language is a dynamically typed language with no type declarations and does not provide static type checking or compile-time checking.
5. Compiled performance: Compared with some compiled languages, the performance of the JavaScript language may be lower. JavaScript is an interpreted language, requiring code to be interpreted at runtime, and the JavaScript virtual machine typically takes longer to start and execute code.

Conclusion:

As a weakly typed, dynamically typed, event-driven programming language, JavaScript language is especially suitable for web applications. Although it does not support multi-threading, blocking IO and native file system access, its flexibility and object-oriented programming characteristics make it a very suitable tool for developing web applications.

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