flt-lib

flt-lib is a JavaScript library for creating and manipulating filter byte arrays compatible with Developer Express's FLT format. It allows converting between a JSON-based filter object and the binary FLT format.

Usage

To convert between FLT files and JSON:

# Convert a JSON file to FLT (using example.js)
node example.js

The library provides functions for converting a JSON filter object to FLT files and vice versa. It supports various comparison operations and logical operations, defined in constants.js.

Example JSON Filter

{
  "operation": "OR",
  "conditions": [
    {
      "type": "condition",
      "value": "prefix%",
      "matchType": "LIKE",
      "row": 1
    },
    {
      "type": "group",
      "operation": "AND",
      "conditions": [
        {
          "type": "condition",
          "value": ["X", "Y"],
          "matchType": "IN_LIST",
          "row": 2
        },
        {
          "type": "condition",
          "value": "100",
          "matchType": "BIGGER_EQUALS",
          "row": 3
        }
      ]
    }
  ]
}

Testing

To run the tests, execute the following command:

npm test

This will run the tests defined in lib.test.js.

CJS Consumer Guide

Installation

npm install flt-lib

Core API

const {
  jsonToByteArray, // Convert JSON filter to FLT byte array
  saveUint8ArrayToFile, // Save byte array to .flt file
  parseFlt // Parse FLT bytes to JSON
} = require('flt-lib');

Supported Operations and Match Types

The library provides the following operations and match types:

Supported Logical Operations

• AND
• OR
• NAND
• NOR

Supported Comparison Operations

• EQUALS
• NOT_EQUALS
• SMALLER
• SMALLER_EQUALS
• BIGGER
• BIGGER_EQUALS
• LIKE
• NOT_LIKE
• BETWEEN
• NOT_BETWEEN
• IN_LIST
• NOT_IN_LIST
• CONTAINS
• NOT_CONTAINS
• STARTS_WITH
• ENDS_WITH

Basic Usage

// 1. Create a filter object
const filter = {
  operation: 'OR',
  conditions: [{
    type: 'condition',
    value: ['A', 'B', 'C'],
    matchType: 'IN_LIST',
    row: 2
  }]
};

// 2. Convert to FLT format
const fltBytes = jsonToByteArray(filter);
saveUint8ArrayToFile(fltBytes, 'filter.flt');

// 3. Read and convert back
const restoredFilter = byteArrayToJson(fltBytes);

Advanced Patterns

Validation

try {
  const parsed = parseFlt(fltBytes);
} catch (error) {
  console.error('Invalid FLT format:', error);
}

Testing Methodology

The library verifies round-trip conversion integrity:

1. Sort object keys consistently
2. Compare JSON representations
3. Validate binary serialization

Run tests with:

npm test

Best Practices

1. Validate FLT bytes with parseFlt()
2. Prefer IN_LIST over multiple EQUALS conditions
3. Use groups for complex nested logic