题解 | #简易计算器#

var Calculator = {
    init: function () {
        var that = this;
        if (!that.isInited) {
            that.isInited = true;
            // 保存操作信息
            // total: Number, 总的结果
            // next: String, 下一个和 total 进行运算的数据
            // action: String, 操作符号
            that.data = {total: 0, next: '', action: ''};
            that.bindEvent();
        }
    },
    bindEvent: function () {
        var that = this;
        // 请补充代码：获取 .cal-keyboard 元素
        var keyboardEl = document.querySelector('.cal-keyboard .cal-items');
        keyboardEl && keyboardEl.addEventListener('click', function (event) {
            // 请补充代码：获取当前点击的dom元素
            var target = event.target;
            if (target.tagName !== 'LI') return

            // 请补充代码：获取target的 data-action 值
            var action = target.dataset.action;
            // 请补充代码：获取target的内容
            var value = target.innerText;
            if (action === 'num' || action === 'operator') {
                that.result(value, action === 'num');
            }
        });
    },
    result: function (action, isNum) {
        var that = this;
        var data = that.data;
        if (isNum) {
            data.next = data.next === '0' ? action : (data.next + action);
            !data.action && (data.total = 0);
        } else if (action === '清空') {
            // 请补充代码：设置清空时的对应状态
            data.total = 0;
            data.next = 0;
            data.action = 0;
        } else if (action === '=') {
            if (data.next || data.action) {
                data.total = that.calculate(data.total, data.next, data.action);
                data.next = '';
                data.action = '';
            }
        } else if (!data.next) {
            data.action = action;
        } else if (data.action) {
            data.total = that.calculate(data.total, data.next, data.action);
            data.next = '';
            data.action = action;
        } else {
            data.total = +data.next || 0;
            data.next = '';
            data.action = action;
        }

        // ���补充代码：获取 .origin-value 元素
        var valEl = document.getElementsByClassName('origin-value')[0];
        valEl && (valEl.innerHTML = data.next || data.total || '0');
    },
    calculate: function (n1, n2, operator) {
        n1 = +n1 || 0;
        n2 = +n2 || 0;
        if (operator === '÷') {
            // 请补充代码：获取除法的结果
            return n1/n2;
        } else if (operator === 'x') {
            // 请补充代码：获取乘法的结果
            return n1*n2;
        } else if (operator === '+') {
            // 请补充代码：获取加法的结果
            return n1+n2;
        } else if (operator === '-') {
            // 请补充代码：获取减法的结果
            return n1-n2;
        }
    }
};
Calculator.init();