What are immediate functions in JavaScript?

Immediate functions in JavaScript are functions that execute automatically as soon as they are defined. They are also known as Immediately Invoked Function Expressions (IIFEs). These functions help create private scope and avoid polluting the global namespace.

Syntax

(function() {
    // Code here executes immediately
})();

// Alternative syntax
(function() {
    // Code here executes immediately
}());

Basic Example

<script>
(function() {
    var message = "Hello from IIFE!";
    console.log(message);
})();

// This variable is not accessible outside
// console.log(message); // Would cause an error
</script>

Hello from IIFE!

Comparison: Regular Function vs IIFE

Here's how a regular function differs from an immediate function:

<script>
// Regular function - needs to be called
function regularFunction() {
    var str = "I need to be called";
    console.log(str);
}
regularFunction(); // Must call explicitly

// IIFE - executes immediately
(function() {
    var str = "I execute automatically";
    console.log(str);
})();
</script>

I need to be called
I execute automatically

IIFE with Parameters

<script>
var name = 'Amit';
(function(studentName) {
    console.log('Student name = ' + studentName);
})(name);
</script>

Student name = Amit

Key Benefits

Common Use Cases

<script>
// Creating a module pattern
var myModule = (function() {
    var privateVar = "I'm private";
    
    return {
        publicMethod: function() {
            console.log("Accessing: " + privateVar);
        }
    };
})();

myModule.publicMethod();
</script>

Accessing: I'm private

Conclusion

Immediate functions (IIFEs) execute automatically and create private scope, preventing global namespace pollution. They're essential for module patterns and avoiding variable conflicts in JavaScript applications.