Typescript anonymous functions

Angular typescript anonymous functions - free examples & tutorial

Learn how to create anonymous fucntion in typescript.

Explanation

Probably you already know that in JavaScript you can define functions like the one below:

        
            
      // Named function
      function add(x, y) {
          return x + y;
      }
      
      // Call named function
      console.log(add(5,10));
      
        
    

which are so-called Named functions. You can also use Anonymous functions:

        
            
      // Anonymous function
      let myAdd = function(x, y) { return x + y; };
      
      // You can call it like this
      console.log(myAdd(5,10));
      
      // But definitely more common
      console.log ((function(x , y) {
        return x + y;
      })(5,10));
      
        
    

An anonymous function is a function that was declared without any named identifier to refer to it. As such, an anonymous function is usually not accessible after its initial creation.

One common use for Anonymous functions is as arguments to other functions. Another common use is as a closure, for which see also the Closures chapter. Below shows its use as an argument to other functions:

        
            
      // Named function
      setTimeout(function() {
        alert('hello');
      }, 1000);
      
        
    

Or call it with parameter:

        
            
      (function(message) {
        alert(message);
      }('foo'));
      
        
    

So basically, you want to use Anonymous functions in all places where you have to use a function as an argument to other function or as a closure (we will learn about closures in later lessons).

In those cases you use the function only once, therefore you don't want to name it (like you would for a Named function) just to use it in a single line.

Anonymous functions might look confusing at the start, however, once you start using them you will find them very handy. But there is something else, another type of the function called an arrow function which we will learn about in the next lesson.