2.2 Callbacks



Using Callbacks is one way to implement asynchronous programming in Javascript. A callback is a function that is passed to another function and executes when some condition is met. As a simple example, say we want make a function that asks for the user's name and then greets the user:
function greeting(name) { alert('Hello ' + name); } function processUserInput(callback) { var name = prompt('Please enter your name.'); callback(name); } processUserInput(greeting);
Here, processUserInput() takes a function as its input. After asking the user for their name, the callback function is invoked and passed the user's name as input.
In this case, greeting() is passed to processUserInput(). Greeting() takes the user's name and displays it.

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