js面向对象实现计数器

使用构造函数实现计数器

通过构造函数创建一个计数器对象，包含计数属性和增减方法：

function Counter() {
    this.count = 0;

    this.increment = function() {
        this.count++;
    };

    this.decrement = function() {
        this.count--;
    };

    this.getValue = function() {
        return this.count;
    };
}

const counter = new Counter();
counter.increment();
console.log(counter.getValue()); // 输出1

使用ES6类实现计数器

采用class语法糖实现更简洁的计数器类：

class Counter {
    constructor() {
        this.count = 0;
    }

    increment() {
        this.count += 1;
    }

    decrement() {
        this.count -= 1;
    }

    getValue() {
        return this.count;
    }
}

const counter = new Counter();
counter.increment();
counter.increment();
console.log(counter.getValue()); // 输出2

使用闭包实现私有计数器

通过IIFE和闭包实现带私有变量的计数器：

const Counter = (function() {
    let count = 0;

    return {
        increment: function() {
            count++;
        },
        decrement: function() {
            count--;
        },
        getValue: function() {
            return count;
        }
    };
})();

Counter.increment();
console.log(Counter.getValue()); // 输出1

带步长的计数器实现

扩展计数器功能，支持自定义步长：

class StepCounter {
    constructor(step = 1) {
        this.count = 0;
        this.step = step;
    }

    increment() {
        this.count += this.step;
    }

    decrement() {
        this.count -= this.step;
    }

    setStep(newStep) {
        this.step = newStep;
    }
}

const counter = new StepCounter(2);
counter.increment();
console.log(counter.count); // 输出2

使用原型链共享方法

通过原型链实现方法共享，节省内存：

function Counter() {
    this.count = 0;
}

Counter.prototype.increment = function() {
    this.count++;
};

Counter.prototype.decrement = function() {
    this.count--;
};

const c1 = new Counter();
const c2 = new Counter();
c1.increment();
console.log(c1.count); // 输出1
console.log(c2.count); // 输出0