Is there any good example of use cases for angular.identity()?

Question

According to the documentation

A function that returns its first argument. This function is useful when writing code in the functional style.

I

Answer 1

Correct me if I'm wrong, but my understanding is that this

function transformer(transformationFn, value) {
  return (transformationFn || angular.identity)(value);
};

could be "un-refactored" to this

function transformer(transformationFn, value) {
  if (transformationFn) {
    return transformationFn(value);
  } else {
    return angular.identity(value);
  }
};

which would be functionally equivalent to this identity-less version:

function transformer(transformationFn, value) {
  if (transformationFn) {
    return transformationFn(value);
  } else {
    return value;
  }
};

So I guess the use case would be when you want to apply a certain transformation to a value when you're supplied with something that may or may not actually exist.

I wanted to better explain the identity function (as I understand it), although as I review my answer I don't think I really answered your question. Leaving my answer here anyway in case it's helpful.