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How TypeScript Compiler Parses Through TypeScript Code

The compiler starts by parsing the TypeScript source code(.tsfiles) into an Abstract Syntax Tree (AST).

Abstract Syntax Tree (AST)

The AST represents the structure and syntax of the source code in a tree-like format. During the parsing phase, the compiler also performs syntax and lexical analysis to identify potential syntax errors.

An Abstract Syntax Tree (AST) is a tree representation of the syntactic structure of source code written in a programming language like TypeScript. During the TypeScript compilation process, the TypeScript compiler first parses the source code into tokens, and then organizes these tokens into an AST. This AST is a hierarchical structure that represents the syntax of the source code while abstracting away the actual text. It makes it easier for the compiler to perform semantic analysis, optimization, and eventually generate the target code (JavaScript in the case of TypeScript).

Here's an example of a simple TypeScript code snippet and its corresponding AST representation using a tree diagram in Markdown and Mermaid.

TypeScript code snippet:

function add(a: number, b: number): number {
return a + b;

A Tree Diagram presenting the AST:

AST Diagram:

|-- Identifier: add
|-- Parameters
| |-- Parameter: a
| | |-- Type: number
| |-- Parameter: b
| | |-- Type: number
|-- ReturnType: number
|-- Block
|-- ReturnStatement
|-- BinaryExpression: a + b
|-- Identifier: a
|-- PlusToken
|-- Identifier: b
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