在javascript中存储函数内部的函数执行

(function() {
    var privateVar = "I am private";
    console.log(privateVar);
})();

function fetchData(url, callback) {
    setTimeout(function() {
        var data = "Fetched data from " + url;
        callback(data);
    }, 1000);
}

fetchData("https://example.com", function(data) {
    console.log(data); // 输出: Fetched data from https://example.com
});

var Module = (function() {
    var privateVar = "Private";

    function privateMethod() {
        console.log(privateVar);
    }

    return {
        publicMethod: function() {
            privateMethod();
        }
    };
})();

Module.publicMethod(); // 输出: Private

function createClosure() {
    var largeData = new Array(1000000).fill('some data');
    return function() {
        console.log(largeData);
    };
}

var closure = createClosure();
closure(); // 使用闭包
largeData = null; // 解除引用，帮助垃圾回收