# Logical Expression Parser

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This is a logical expression parser for TypeScript, it can parse a logical expression into a AST object and evaluates the result using your token checking function.

It's original developed by NimitzDEV: 
https://github.com/NimitzDEV/logical-expression-parser

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### Improvements compared to the original:
- typescript support
- custom logical operators

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#### [Default] logical operators
 - `/` Or
 - `&` And
 - `!` Not
 - `()` Parentheses

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## How it works
1. The parser parse and tokenize the expression, for example one of your function requires `REGISTERED&(SPECIAL/INVITED)`
1. Parser then will pass `REGISTERED`, `SPECIAL` and `INVITED` into your token checking function to get a boolean result
1. Finaly the parser will evaluates the final result

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## Examples
```typescript
  const { evaluate } = ExpressionParserFactory.init().build();
  const result1 = evaluate("REGISTERED&(SPECIAL/INVITED)", ["REGISTERED", "INVITED"]); // --> true
  const result2 = evaluate("REGISTERED&(SPECIAL/INVITED)", ["REGISTERED"]); // --> false
```
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use custom operators if needed:
```typescript

  const { evaluate } = ExpressionParserFactory.init()
    .setToken(Token.OPERATOR_AND, '+')
    .setToken(Token.OPERATOR_NOT, '-')
    .setToken(Token.OPERATOR_OR, '|')
    .setToken(Token.PARENTHESES_OPEN, '{')
    .setToken(Token.PARENTHESES_CLOSE, '}')
    .build();

  const result = evaluator.evaluate("{A+C}|{B&-C}", ['A', 'B'])
```