SOURCE

$(function() {

    function Calculator($dom) {
        this.$dom = $($dom);
        // 历史运算
        this.$history = this.$dom.find('.calc-history');
        // 输入区
        this.$in = this.$dom.find('.calc-in');
        // 输出区
        this.$out = this.$dom.find('.calc-out');
        this.$operation = this.$dom.find('.calc-operation');

        // 运算符映射
        this.op = {
            'plus': '+',
            'minus': '-',
            'mul': '*',
            'div': '/'
        };
        this.opArr = ['+', '-', '*', '/'];

        // 中缀表达式
        this.infix = [];
        // 后缀表达式
        this.suffix = [];
        // 后缀表达式运算结果集
        this.result = [];
        // 存储最近的值
        this.lastVal = 0;
        // 当前已经计算等于完成
        this.calcDone = false;
        // 当前正在进行小数点点（.）相关值的修正
        this.curDot = false;

        this.init();
    }

    Calculator.prototype = {
        constructor: Calculator,
        // 初始化
        init: function() {
            this.bindEvent();
        },
        // 绑定事件
        bindEvent: function() {
            var that = this;

            that.$operation.on('click', function(e) {
                e = e || window.event;
                var elem = e.target || e.srcElement,
                    val,
                    action;

                if (elem.tagName === 'TD') {
                    val = elem.getAttribute('data-val') || elem.getAttribute('data-ac');
                    // 数字：0-9
                    if (!isNaN(parseInt(val, 10))) {
                        // 构建中缀表达式并显示
                        var infixRe = that.buildInfix(parseInt(val, 10), 'add');
                        that.$in.text(infixRe.join('')).addClass('active');

                        that.calculate();

                        return;
                    }

                    action = val;

                    // 操作：清除、删除、计算等于
                    if (['cls', 'del', 'eq'].indexOf(action) !== -1) {
                        if (!that.infix.length) {
                            return;
                        }

                        // 清空数据
                        if (action === 'cls' || (action === 'del' && that.calcDone)) {
                            that.$in.text('');
                            that.$out.text('');

                            that.resetData();
                        }
                        // 清除
                        else if (action === 'del') {
                            // 重新构建中缀表达式
                            var infixRe = that.buildInfix(that.op[action], 'del');
                            that.$in.text(infixRe.join('')).addClass('active');

                            that.calculate();

                        }
                        // 等于
                        else if (action === 'eq') {
                            that.calculate('eq');

                        }
                    }
                    // 预运算：百分比、小数点、平方
                    else if (['per', 'dot', 'sq'].indexOf(action) !== -1) {
                        if (!that.infix.length || that.isOp(that.lastVal)) {
                            return;
                        }

                        if (action === 'per') {
                            that.lastVal /= 100;
                        } else if (action === 'sq') {
                            that.lastVal *= that.lastVal;
                        } else if (action === 'dot') {
                            // that.curDot = true;
                        }

                        // 重新构建中缀表达式
                        var infixRe = that.buildInfix(that.lastVal, 'change');
                        that.$in.text(infixRe.join('')).addClass('active');

                        that.calculate();
                    }
                    // 运算符：+ - * /
                    else if (that.isOp(that.op[action])) {
                        if (!that.infix.length && (that.op[action] === '*' || that.op[action] === '/')) {
                            return;
                        }

                        var infixRe = that.buildInfix(that.op[action], 'add');
                        that.$in.text(infixRe.join('')).addClass('active');
                    }
                }
            });
        },

        resetData: function() {
            this.infix = [];
            this.suffix = [];
            this.result = [];
            this.lastVal = 0;
            this.curDot = false;
        },

        // 构建中缀表达式
        buildInfix: function(val, type) {
            // 直接的点击等于运算之后，
            if (this.calcDone) {
                this.calcDone = false;
                // 再点击数字，则进行新的运算
                if (!this.isOp(val)) {
                    this.resetData();
                }
                // 再点击运算符，则使用当前的结果值继续进行运算
                else {
                    var re = this.result[0];
                    this.resetData();
                    this.infix.push(re);
                }

            }

            var newVal;

            // 删除操作
            if (type === 'del') {
                newVal = this.infix.pop();
                // 删除末尾一位数
                newVal = Math.floor(newVal / 10);
                if (newVal) {
                    this.infix.push(newVal);
                }

                this.lastVal = this.infix[this.infix.length - 1];
                return this.infix;
            }
            // 添加操作，首先得判断运算符是否重复
            else if (type === 'add') {
                // 两个连续的运算符
                if (this.isOp(val) && this.isOp(this.lastVal)) {
                    return this.infix;
                }
                // 两个连续的数字
                else if (!this.isOp(val) && !this.isOp(this.lastVal)) {
                    newVal = this.lastVal * 10 + val;
                    this.infix.pop();
                    this.infix.push(this.lastVal = newVal);

                    return this.infix;
                }
                // 首个数字正负数
                if (!this.isOp(val) && this.infix.length === 1 && (this.lastVal === '+' || this.lastVal === '-')) {
                    newVal = this.lastVal === '+' ? val : 0 - val;
                    this.infix.pop();
                    this.infix.push(this.lastVal = newVal);

                    return this.infix;
                }

            // TODO: 小数点运算
            //     if (this.isOp(val)) {
            //         this.curDot = false;
            //     }

            //     // 小数点
            //     if (this.curDot) {
            //         var dotLen = 0;
            //         newVal = this.infix.pop();
            //         dotLen = newVal.toString().split('.');
            //         dotLen = dotLen[1] ? dotLen[1].length : 0;

            //         newVal +=  val / Math.pow(10, dotLen + 1);
            //         // 修正小数点运算精确值
            //         newVal = parseFloat(newVal.toFixed(dotLen + 1));

            //         this.infix.push(this.lastVal = newVal);
            //         return this.infix;
            //     }

                this.infix.push(this.lastVal = val);
                return this.infix;
            }

            // 更改操作，比如%的预运算
            else if (type === 'change') {
                this.infix.pop();
                this.infix.push(this.lastVal = val);

                return this.infix;
            }

        },
        // 判断是否为运算符
        isOp: function(op) {
            return op && this.opArr.indexOf(op) !== -1;
        },
        // 判断运算符优先级
        priorHigher: function(a, b) {
            return (a === '+' || a === '-') && (b === '*' || b === '/');
        },
        // 进行运算符的运算
        opCalc: function(b, op, a) {
            return op === '+'
                ? a + b
                : op === '-'
                ? a - b
                : op === '*'
                ? a * b
                : op === '/'
                ? a / b
                : 0;
        },
        // 即时得进行运算
        calculate: function(type) {
            this.infix2Suffix();
            var suffixRe = this.calcSuffix();

            if (suffixRe) {
                this.$out.text('=' + suffixRe)
                    .attr('title', suffixRe)
                    .removeClass('active');

                // 如果是直接显示地进行等于运算
                if (type === 'eq') {
                    this.$in.removeClass('active');
                    this.$out.addClass('active');
                    // 设置标记：当前已经显示地进行计算
                    this.calcDone = true;
                    this.lastVal = suffixRe;
                    // 设置历史记录
                    var history = this.infix.join('') + ' = ' + suffixRe;
                    this.$history.text(history).attr('title', history);
                }

            }
        },

        // 中缀表达式转后缀
        infix2Suffix: function() {
            var temp = [];
            this.suffix = [];

            for (var i = 0; i < this.infix.length; i++) {
                // 数值，直接压入
                if (!this.isOp(this.infix[i])) {
                    this.suffix.push(this.infix[i]);
                }
                else {
                    if (!temp.length) {
                        temp.push(this.infix[i]);
                    }
                    else {
                        var opTop = temp[temp.length - 1];
                        // 循环判断运算符优先级，将运算符较高的压入后缀表达式
                        if (!this.priorHigher(opTop, this.infix[i])) {
                            while (temp.length && !this.priorHigher(opTop, this.infix[i])) {
                                this.suffix.push(temp.pop());
                                opTop = temp[temp.length - 1];
                            }
                        }
                           // 将当前运算符也压入后缀表达式
                        temp.push(this.infix[i]);
                    }
                }
            }
            // 将剩余运算符号压入
            while (temp.length) {
                this.suffix.push(temp.pop());
            }
        },

        // 后缀表达式计算
        calcSuffix: function() {
            this.result = [];

            for (var i = 0; i < this.suffix.length; i++) {
                // 数值，直接压入结果集
                if (!this.isOp(this.suffix[i])) {
                    this.result.push(this.suffix[i]);
                }
                // 运算符，从结果集中取出两项进行运算，并将运算结果置入结果集合
                else {
                    this.result.push(this.opCalc(this.result.pop(), this.suffix[i], this.result.pop()));
                }
            }
            // 此时结果集中只有一个值，即为结果
              return this.result[0];
        }
    };

    new Calculator('.calc-wrap');
});

<h5>计算计算</h5>
    <!-- 计算器 -->
    <div class="calc-wrap">
        <div class="calc-in-out">
            <!-- 上一条运算记录 -->
            <p class="calc-history" title=""></p>
            <!-- 输入的数据 -->
            <p class="calc-in"></p>
            <!-- 输出的运算结果 -->
            <p class="calc-out active"></p>
        </div>
        <table class="calc-operation">
            <thead></thead>
            <tbody>
                <tr>
                    <td data-ac="cls" class="cls">C</td>
                    <td data-ac="del">&larr;</td>
                    <td data-ac="sq">x<sup>2</sup></td>
                    <td data-ac="mul">&times;</td>
                </tr>
                <tr>
                    <td data-val="7">7</td>
                    <td data-val="8">8</td>
                    <td data-val="9">9</td>
                    <td data-ac="div">&divide;</td>
                </tr>
                <tr>
                    <td data-val="4">4</td>
                    <td data-val="5">5</td>
                    <td data-val="6">6</td>
                    <td data-ac="plus">+</td>
                </tr>
                <tr>
                    <td data-val="1">1</td>
                    <td data-val="2">2</td>
                    <td data-val="3">3</td>
                    <td data-ac="minus">-</td>
                </tr>
                    <td data-ac="per">%</td>
                    <td data-val="0">0</td>
                    <td data-ac="dot">.</td>
                    <td data-ac="eq" class="eq">=</td>
            </tbody>
        </table>
    </div>

body {
    padding: 20px;
    font-family: Arial;
  
}

.calc-wrap {
    width: 300px;
    border: 1px solid #ddd;
    border-radius: 3px;
}


.calc-operation {
    width: 100%;
    border-collapse: collapse;
}

.calc-in-out {
    width: 100%;
    padding: 10px 20px;
    text-align: right;
    box-sizing: border-box;
    background-color: rgba(250, 250, 250, .9);
}
.calc-in-out p {
    overflow: hidden;
    margin: 5px;
    width: 100%;
}
.calc-history {
    margin-left: -20px;
    font-size: 18px;
    color: #bbb;
    border-bottom: 1px dotted #ddf;
    min-height: 23px;
}

.calc-in,
.calc-out {
    font-size: 20px;
    color: #888;
    line-height: 39px;
    min-height: 39px;
}

.calc-in {
    color: #888;
}
.calc-out {
    color: #ccc;
}

.calc-in.active,
.calc-out.active {
    font-size: 34px;
    color: #666;
}

.calc-operation td {
    padding: 10px;
    width: 25%;
    text-align: center;
    border: 1px solid #ddd;
    font-size: 26px;
    color: #888;
    cursor: pointer;
}

.calc-operation td:active {
    background-color: #ddd;
}

.calc-operation .cls {
    color: #ee8956;
}

CSS样式