How does the load() function allow the user to provide a callback?

Question

In javascript it\'s very popular for libraries/frameworks to let us define a callback function for post-processing of data.

eg.

load(\"5\", function(         


        

Answer 1

Well, the load function could look like this:

function load(arg, callback) {

  var element = { name: "foo " + arg }; // something to pass

  if (typeof callback == 'function') {
    callback(element);
  }
}

With the typeof check we make sure that the callback argument is an object that we can invoke, a function.

Then your example:

load("5", function(element) {
    alert(element.name); // Will show `"foo 5"`.
});