Programming Tutorials

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IIFE in JavaScript

By: Urmila in Javascript Tutorials on 2023年04月26日 [フレーム]

IIFE stands for Immediately Invoked Function Expression. It's a way to create a self-executing function in JavaScript. The main idea is to write a function that is executed immediately after it's defined.

Here's an example of an IIFE:

(function () {
 console.log('This function is immediately executed');
})();

In this example, we create an anonymous function using the function keyword and wrap it in parentheses. Then we immediately call it by appending parentheses after the closing curly brace. This function logs the message "This function is immediately executed" to the console.

IIFEs are often used to create a local scope for variables, so they don't pollute the global namespace. Here's an example:

(function () {
 var message = 'Hello';
 console.log(message);
})();
console.log(message); // This will throw a ReferenceError, because message is not defined in the global scope

In this example, we define a variable message inside an IIFE. This variable is local to the IIFE, and it's not accessible outside of it. If we try to access message outside of the IIFE, we'll get a ReferenceError.

IIFEs can also take arguments, just like any other function. Here's an example:

(function (a, b) {
 console.log(a + b);
})(2, 3); // This will log 5 to the console

In this example, we define an IIFE that takes two arguments a and b, and logs their sum to the console. We immediately call the IIFE and pass in the values 2 and 3. The IIFE logs 5 to the console, because a + b equals 5.