Principles.md

Avoid functionality injection (WIP)

Bad

function flexibleFunction(data, readFirstOnly = false) {
    
}

Never overwrite data when reading inputs

const source1 = {
  a: 123,
  b: 456,
};

const source2 = {
  a: 987,
  c: 654, 
};

function createBadConsumer() {
  const data = {};
  return {
    consume(source) {
      Object.assign(data, source);
    },
    show(key) {
      return data[key];
    }
  }
}

function createGoodConsumer() {
  const sources = [];
  return {
    consume(source) {
      sources.push(source);
    },
    show(key) {
      for (const source of sources) {
        if (source[key]) {
          return source[key];
        }
      }
    }
  }
}

Diagnosing why show() is giving the wrong data is much more likely to obscure the error.