What is the purpose of the typedef keyword in Dart?

Used for creating type aliases. This allows giving a new, more understandable name to an existing type or function signature, enhancing code readability and flexibility.

Main usage scenarios:

• Type aliases for functions: Creating a pseudonym for a complex function signature.

  // Define a typedef for a function that takes a string and returns an int
  typedef StringToInt = int Function(String s);
  
  // Use typedef when declaring a variable or parameter
  StringToInt myConverter = (String source) => source.length;
  

• Type aliases for collections: Simplifying long and complex collection type descriptions (e.g., Map<String, Map<int, List<double>>>).

  // Define a typedef for a complex Map type
  typedef NestedMap = Map<String, Map<int, List<double>>>;
  
  // Use typedef for a variable
  NestedMap data = {
    'key1': {
      1: [1.1, 1.2],
      2: [2.1]
    },
  };
  

• Improving readability and refactoring: Hiding implementation details of a type under a more abstract name.