js 闭包的缺点

function createClosure() {
    let largeArray = new Array(1000000).fill('some data');
    return function() {
        console.log(largeArray[0]);
    };
}

let closure = createClosure();
// largeArray 会一直存在于内存中，直到 closure 不再被引用

function createFunctions() {
    let functions = [];
    for (var i = 0; i < 5; i++) {
        functions.push(function() {
            console.log(i);
        });
    }
    return functions;
}

let funcs = createFunctions();
funcs.forEach(func => func()); // 输出 5 五次，而不是 0 到 4

function createFunctions() {
    let functions = [];
    for (let i = 0; i < 5; i++) { // 使用 let 声明
        functions.push(function() {
            console.log(i);
        });
    }
    return functions;
}

let funcs = createFunctions();
funcs.forEach(func => func()); // 输出 0 到 4