Briefly describe the specific processing process of JavaScript

JavaScript is an advanced client-side scripting language that is widely used in web front-end development. It can run in the user's browser to achieve dynamic interaction and control of page effects. In this article, we will briefly describe the specific processing process of JavaScript to help readers better understand and use JavaScript.

1. Lexical analysis

When writing JavaScript code, you need to use some keywords and grammatical structures. These keywords and grammatical structures have fixed meanings in JavaScript. . Before running JavaScript code, the code needs to be lexically analyzed. The purpose of lexical analysis is to analyze the code into grammatical units, such as keywords, identifiers, operators, etc., for subsequent grammatical analysis.

2. Grammar Analysis

After lexical analysis is completed, the code will be passed to the parser for grammar analysis. The purpose of syntax analysis is to verify whether the code complies with the JavaScript language specification and convert the code into an abstract syntax tree (AST). An abstract syntax tree is a tree-like structure that clearly represents the semantic and logical structure of the code. On subsequent runs, the JavaScript engine will execute the code based on the AST.

3. Preprocessing

Before the JavaScript code is run, some preprocessing is required. The main purpose of preprocessing is to identify and process variables and functions in the code. During the preprocessing process, the JavaScript engine will create global variable objects and function objects and store them in memory for subsequent reference and call.

4. Execute code

When running, the JavaScript engine will execute each node in the abstract syntax tree, including statements, expressions, function calls, etc. During the execution of the code, the JavaScript engine will perform calculations, comparisons, logical judgments and other operations based on the logic written by the programmer, and finally output the calculation results or change the display effect of the page.

5. Garbage Collection

JavaScript is a dynamic language that supports the dynamic creation and destruction of variables and objects. During the execution of the code, the JavaScript engine will continuously create new objects and variables and destroy them after use or when they are no longer needed. In order to avoid memory overflow, the JavaScript engine also needs to perform garbage collection, release objects and variables that are no longer used, and reclaim memory.

Summary

The above is the specific processing process of JavaScript code. Understanding the execution process of JavaScript helps us better understand and use the language, and also helps us write more efficient and optimized code. In addition, we also need to pay attention to JavaScript language specifications and best practices to ensure the maintainability and readability of the code.

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