Learning TypeScript 2.x - Second Edition

Functions

Just as in JavaScript, TypeScript functions can be created either as a named function or as an anonymous function, which allows us to choose the most appropriate approach for an application, whether we are building a list of functions in an API or a one-off function to hand over to another function:

// named function 
function greet(name?: string): string { 
  if(name){ 
    return "Hi! " + name; 
  } else { 
    return "Hi!"; 
  } 
} 
 
// anonymous function 
let greet = function(name?: string): string { 
  if (name) { 
    return "Hi! " + name; 
  } else { 
    return "Hi!"; 
  } 
} 

As we can see in the preceding code snippet, in TypeScript, we can add types to each of the parameters and then to the function itself to add a return type. TypeScript can infer the return type ...