What are immediate functions in JavaScript?

The immediate function executes as soon as it is defined. To understand the role of immediate function, let’s see the difference between a function and an immediate function −

Here’s immediate function −

(function() {
   var str = "display";
}());
function display() {
   // this returns undefined
   alert(str);
}

Here’s a function −

var str = "display";
function display() {
   // This returns "display"
   alert(str);
}

Let’s see another example of immediate functions −

var name = 'Amit';
(function(sName) {
   alert( 'Student name = ' + sName );
}(sName))