Anonymous functions in JavaScript are functions that are defined without a name. They are commonly used as arguments to other functions or as immediately invoked function expressions (IIFE).

Here's an example of an anonymous function:

javascriptCopy code// Anonymous function as a callback
setTimeout(function() {
  console.log('This is an anonymous function.');
}, 1000);

In this example, setTimeout is a function that takes another function (the callback) as its first argument. The function passed as an argument is an anonymous function because it doesn't have a name.

Anonymous functions can also be used as IIFE, which are functions that are executed immediately after they are defined. Here's an example:

javascriptCopy code// Immediately Invoked Function Expression (IIFE)
(function() {
  console.log('This is an IIFE.');
})();

In this example, the anonymous function is enclosed within parentheses and followed by () to immediately invoke it.

Anonymous functions are often used in situations where a function is needed temporarily or where a function doesn't need to be referenced by name. They are commonly used in event handling, asynchronous callbacks, and for scoping purposes. Check out the free online JS tutorial for more info like this!