https://github.com/ashokdey/parserts
A parser implemented in pure typescript without any dependencies.
https://github.com/ashokdey/parserts
abstract-syntax-tree parser typescript
Last synced: over 1 year ago
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A parser implemented in pure typescript without any dependencies.
- Host: GitHub
- URL: https://github.com/ashokdey/parserts
- Owner: ashokdey
- License: mit
- Created: 2022-10-01T11:28:57.000Z (over 3 years ago)
- Default Branch: master
- Last Pushed: 2022-10-28T11:51:49.000Z (over 3 years ago)
- Last Synced: 2025-01-28T18:49:41.708Z (over 1 year ago)
- Topics: abstract-syntax-tree, parser, typescript
- Language: TypeScript
- Homepage:
- Size: 227 KB
- Stars: 0
- Watchers: 1
- Forks: 0
- Open Issues: 1
-
Metadata Files:
- Readme: README.md
- License: LICENSE
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README
# ParserTS
### An AST generator implemented in TypeScript
### What Does Parser Mean? source
A parser is a compiler or interpreter component that breaks data into smaller elements for easy translation into another language. A parser takes input in the form of a sequence of tokens, interactive commands, or program instructions and breaks them up into parts that can be used by other components in programming.
A parser usually checks all data provided to ensure it is sufficient to build a data structure in the form of a parse tree or an abstract syntax tree.
In order for the code written in human-readable form to be understood by a machine, it must be converted into machine language. This task is usually performed by a translator (interpreter or compiler). The parser is commonly used as a component of the translator that organizes linear text in a structure that can be easily manipulated (parse tree). To do so, it follows a set of defined rules called “grammar”.
The overall process of parsing involves three stages:
### Lexical Analysis
A lexical analyzer is used to produce tokens from a stream of input string characters, which are broken into small components to form meaningful expressions. A token is the smallest unit in a programming language that possesses some meaning (such as +, -, *, “function”, or “new” in JavaScript).
### Syntactic Analysis
Checks whether the generated tokens form a meaningful expression. This makes use of a context-free grammar that defines algorithmic procedures for components. These work to form an expression and define the particular order in which tokens must be placed.
Semantic Parsing: The final parsing stage in which the meaning and implications of the validated expression are determined and necessary actions are taken.
A parser's main purpose is to determine if input data may be derived from the start symbol of the grammar.
## Examples
```javascript
func add(a, b) {
return a + b;
}
```
The above code will be converted into an AST like:
```json
{
"type": "Program",
"body": [
{
"type": "FunctionDeclaration",
"name": {
"type": "IDENTIFIER",
"name": "add"
},
"params": [
{
"type": "IDENTIFIER",
"name": "a"
},
{
"type": "IDENTIFIER",
"name": "b"
}
],
"body": {
"type": "BlockStatement",
"body": [
{
"type": "ReturnStatement",
"argument": {
"type": "BinaryExpression",
"operator": "+",
"left": {
"type": "IDENTIFIER",
"name": "a"
},
"right": {
"type": "IDENTIFIER",
"name": "b"
}
}
},
{
"type": "EmptyStatement",
"body": null
}
]
}
}
]
}
```
### Upcoming Developments
- Support for function call
- Support for Classes and Objects
- CLI tool
### Usages
- Type your code in the `src/index.ts`
- Run command to produce ast `npm run dev >> ast.json`
### Notes
Thanks to [Dmitry Soshnikov](http://dmitrysoshnikov.com/) for his course on [Programming Languages](https://www.dmitrysoshnikov.education/p/programming-languages-design-ultimate-bundle-2nd-edition)