🧠 JavaScript Syntax Parsers with PLY (Python Lex-Yacc)

This repository contains a collection of mini-parsers for different JavaScript syntax constructs, implemented using the ply library in Python. PLY is a Pythonic re-implementation of the popular compiler construction tools lex and yacc.

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📘 Introduction

Parsing is a crucial step in compilers and interpreters where a stream of tokens (produced by a lexer) is analyzed to determine its grammatical structure according to a formal grammar.

This project breaks down the complexity of JavaScript parsing into smaller, manageable components, each focusing on a specific syntax feature.

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✨ Features

• 🧩 Modular Design – Each JavaScript construct is handled by a separate ply parser.
• 🏷️ Lexical Analysis – Uses ply.lex to tokenize JavaScript input (e.g., ID, VAR, SEMICOLON).
• 🧠 Syntax Analysis – Defines grammar rules via ply.yacc to validate and parse constructs.
• 🖥️ Interactive Input – Each script prompts for input, enabling real-time testing of JavaScript snippets.

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⚙️ Installation

1. Clone the repository

git clone https://github.com/your_username/javascript-ply-parsers.git
cd javascript-ply-parsers

2. Install Dependencies

pip install ply

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🚀 Usage

Each .py file is a standalone parser for a JavaScript feature. To run:

python <parser_filename>.py

You will be prompted to enter JavaScript code.

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🔍 Individual Parsers

📄 Variable Declaration and Assignment (var_declaration_assignment.py)

Handles basic var, let, const declarations and assignments.

✅ Supported Syntax

var x;
let y;
const z;
var a = 10;
let b = myVar;
const c = 20;
var x; x = 5;

▶️ How to Run

python var_declaration_assignment.py

💡 Example Input

var myVariable = 123;
let anotherOne;
const PI = 3.14;
var test; test = 100;

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📦 Array Declaration (array.py)

Focuses on literal and constructor-based array declarations.

✅ Supported Syntax

const myArray = [1, 2, "hello"];
let emptyArray = [];
var newArray = new Array();
let prefilledArray = new Array(1, "test", 3);

▶️ How to Run

python array.py

💡 Example Input

const numbers = [1, 2, 3];
let names = ["Alice", "Bob"];
var data = new Array();
let mixed = new Array("apple", 123, "banana");

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⏱️ setTimeout Function Call (setTimeout.py)

Parses setTimeout function calls with a callback and delay.

✅ Supported Syntax

setTimeout(myFunction, 1000);
setTimeout(anotherFunc, 500);

▶️ How to Run

python setTimeout.py

💡 Example Input

setTimeout(callbackFunction, 2000);
setTimeout(animate, 500);

📌 This parser prints lexed tokens before parsing.

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🔁 For Loop (forloop.py)

Handles basic for loops with optional console.log in the body.

✅ Supported Syntax

for (let i = 0; i < 10; i++) { console.log("Looping"); }
for (var x = 5; x > 0; x--) { console.log("Count"); }

▶️ How to Run

python forloop.py

💡 Example Input

for (let i = 0; i < 5; i++) { console.log("Iteration"); }
for (var j = 10; j > 0; j--) { console.log("Countdown"); }

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