An AST(Abstract Syntax Tree) is a data structure used to represent the syntax of most programs during compilation.

It is used to represent the structure of a program.

This is helpful for tools like compilers, code linters, and interpreters.

Most tools that need to perform operations on a high-level programming language, transform the code into an AST first before analysing or operating on the code.

Ever wondered how your IDE extensions are able to parse and interpret your program?

Well, this is one of the methods used to understand code by other tools(programs).

Below is what an AST looks like in JSON format.

It's simply an object with each node representing a function declaration or a binding(variable declaration).
It also has information about its position in the code, and also details of the variable or function declaration.

Components of an AST

Nodes:

An AST is made up of nodes. Each node represents a syntactic element or construct in the source code. Nodes can correspond to keywords, variables, function calls, operators, and more.

Nodes are organized into a tree-like structure, with a root node representing the entire program or code snippet and child nodes representing smaller language constructs.

AST nodes are typically generated during the parsing phase of a compiler or interpreter.

Traversal:

To perform tasks using an AST, developers build tools that traverse the AST by visiting nodes in a specific order, such as depth-first traversal.

During traversal, actions can be taken based on the type of node being visited.

For example, a linter may check coding style rules, or a compiler may generate machine code instructions.

Source-to-Source Transformations:

ASTs are used in source-to-source transformations, where code is transformed from one representation to another while preserving its functionality.

For example, transpilers like Babel transform modern JavaScript code into an older version for compatibility with older browsers.

Code Analysis and Tooling:

ASTs enable code analysis tools to check for syntax errors, code style violations, and potential bugs.

Static analysis tools can identify security vulnerabilities and performance bottlenecks.

Code editors and IDEs use ASTs to provide features like syntax highlighting, auto-completion, and code navigation.

Language Agnostic:

ASTs are not limited to a single programming language. They can be used for various languages, making them a versatile tool for creating language-specific tools and utilities.

Finally, ASTs are a powerful representation of source code that allows for structured analysis, manipulation, and transformation of code in a way that maintains its syntactic and semantic integrity.

They are a fundamental concept in compiler construction, code analysis, and language tooling and you just learnt about them and how they work.

I'm currently building a tool that makes use of ASTs.
This made me try to understand them better and how they work.
Maybe you can guess what the tool will do?