When a function is passed to another function, it is called a callback function. It goes over this function than to call a passed function.
Example
You can try to run the following code to learn how to work with callback functions −
<html>
<head>
<script>
var callback = function(myCallback) {
setTimeout(function() {
myCallback();
}, 5000);
};
document.write("First is displayed");
document.write("<br>Second is displayed");
callback(function() {
document.write("This is Callback function");
});
document.write("<br>Last is displayed");
</script>
</head>
</html>