What is an anonymous function in js

Anonymous function is a function without a name in JavaScript. It is usually used as a callback function or an immediate execution function expression. It is characterized by having no name, accepting parameters, and returning a value. Uses include callback functions, IIFEs, module patterns, and event handlers.

What are JavaScript anonymous functions?

Anonymous functions are functions in JavaScript that have no name. They are often used as callback functions or immediately executed function expressions (IIFE).

Features:

• No name
• Define with keyword function, followed by parentheses and function body
• Can receive parameters and return values ​​
• Usually used interchangeably with arrow functions (ES6)

Usage:

• Callback function: Passed to other functions as parameters and executed when a specific event occurs.
• Immediately executed function expression (IIFE): Used to encapsulate code and execute it when called immediately.
• Module mode: Used to create private scopes and prevent global pollution.
• Event handler: Used to respond to user interaction or DOM events.

Example:

// 匿名回调函数
const callback = function (event) {
  // 执行回调逻辑
};

// IIFE
(function () {
  // 立即执行的代码
})();

// 模块模式
const module = (function () {
  // 私有变量和方法
  return {
    // 公共 API
  };
})();

// 事件处理程序
document.getElementById("button").addEventListener("click", function (event) {
  // 处理点击事件
});

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