larry vibe coding demo - prompt 1

md

We have some code:  
  
**bjj_calculate_match_difficulty.js**  
  
```js  
function calculateMatchDifficulty(practitioner1, practitioner2) {
    const beltRanks = ['white', 'blue', 'purple', 'brown', 'black'];
    // Calculate the difference in belt ranks
    const beltDiff = beltRanks.indexOf(practitioner2.belt) - beltRanks.indexOf(practitioner1.belt);
    // Calculate the cumulative effect of age, weight, and height
    let ageDiff = (practitioner1.age - practitioner2.age) / 10;
    let weightDiff = (practitioner2.weightInPounds - practitioner1.weightInPounds) / 20;
    let heightDiff = (practitioner2.heightInInches - practitioner1.heightInInches) / 6;
    let cumulativeEffect = ageDiff + weightDiff + heightDiff;
    console.log(`ageDiff=${ageDiff}`);
    console.log(`weightDiff=${weightDiff}`);
    console.log(`heightDiff=${heightDiff}`);
    console.log(`beltDiff=${beltDiff}`);
    // Return the cumulative effect as a floating-point number
    return (beltDiff + cumulativeEffect) * -1;
}
```  
  
And we have some unit tests written in swift:  
  
```swift  
//
//  BjjTests.swift
//  
//
//
import XCTest
@testable import bjjCalculateMatchDifficulty
final class BjjTests: XCTestCase {
  override func setUpWithError() throws {
    // Put setup code here. This method is called before the invocation of each test method in the class.
  }
  override func tearDownWithError() throws {
    // Put teardown code here. This method is called after the invocation of each test method in the class.
  }
  func testParsePractitioner() throws {
    let json = """
    {
      "belt": "white",
      "age": 42,
      "weightInPounds": 175,
      "heightInInches": 69
    }
    """
    let practitioner = try Bjj.parsePractitioner(json: json)
    XCTAssertEqual(practitioner.belt, "white")
    XCTAssertEqual(practitioner.age, 42)
    XCTAssertEqual(practitioner.weightInPounds, 175)
    XCTAssertEqual(practitioner.heightInInches, 69)
  }
  func testCalculateMatchDifficulty() throws {
    let practitioner1 = Bjj.Practitioner(belt: "white", age: 42, weightInPounds: 175, heightInInches: 69)
    let practitioner2 = Bjj.Practitioner(belt: "blue", age: 32, weightInPounds: 195, heightInInches: 75)
    let result = try Bjj.calculateMatchDifficulty(practitioner1: practitioner1, practitioner2: practitioner2)
    XCTAssertEqual(result, -4.0)
  }
  func testCalculateMatchDifficulty2() throws {
    let practitioner1 = Bjj.Practitioner(belt: "white", age: 42, weightInPounds: 175, heightInInches: 69)
    let practitioner2 = Bjj.Practitioner(belt: "blue", age: 25, weightInPounds: 160, heightInInches: 65)
    let result = try Bjj.calculateMatchDifficulty(practitioner1: practitioner1, practitioner2: practitioner2)
    XCTAssertEqual(result, -1.2833333)
  }
}
```  
  
Please transcode the tests to javascript so that our javascript code has unit tests. Use jest.