Disposable Functions

Since I like to use this term (but never found any other source with that wording) I want to describe what a disposable function means to me:

• a lambda-helper-function, which is only invoked inside another function
• is only accessible inside a specific function

With the following benefits:

• helps to avoid code repetition
• describes what it does by its name (cleaner code)
• avoids creating private functions when they are only used exclusively inside one function

Example

function createSerialNumber() {
  let randomString = (length, charPool = 'ABCDEFGHJKLMPQRTUVWXYZ346789') => {
    return Array(length).fill(0).map(() => {
      return charPool[Math.floor(Math.random() * charPool.length)];
    }).join('');
  }
  // Example result: '6YFR-444EPP-3CAB8-3371'
  return `${randomString(4)}-${randomString(6)}-${randomString(5)}-${randomString(4,'346789')}`;
}

In this example, the disposable function is randomString. It's used here four times to create a random String in different length and characters to build a serial number.