//body

<div id="maindiv">
    <lable class="lbname">计算器</lable>
    <div id="content">
        <span id="note"></span>
        <input type="text" onfocus="this.blur();" id="num" value="http://www.mamicode.com/0">
    </div>
    <div id="result">
        <ul>
            <li>
                <lable class="lb1" onclick="sin()">sin</lable>
            </li>
            <li>
                <lable class="lb1" onclick="cos()">cos</lable>
            </li>
            <li>
                <lable class="lb1" onclick="tan()">tan</lable>
            </li>
            <li>
                <lable id="lb5" onclick="clearnum()">AC</lable>
            </li>
        </ul>
    </div>
    <div id="other">
        <ul>
            <li>
                <lable class="lb2" onclick="command(1)">1</lable>
            </li>
            <li>
                <lable class="lb2" onclick="command(2)">2</lable>
            </li>
            <li>
                <lable class="lb2" onclick="command(3)">3</lable>
            </li>
            <li>
                <lable class="lb3" onclick="plus()">+</lable>
            </li>
            <li>
                <lable class="lb3" onclick="jian()">-</lable>
            </li>
        </ul>
        <ul>
            <li>
                <lable class="lb2" onclick="command(4)">4</lable>
            </li>
            <li>
                <lable class="lb2" onclick="command(5)">5</lable>
            </li>
            <li>
                <lable class="lb2" onclick="command(6)">6</lable>
            </li>
            <li>
                <lable class="lb3" onclick="chen()">*</lable>
            </li>
            <li>
                <lable class="lb3" onclick="chu()">/</lable>
            </li>
        </ul>
        <ul>
            <li>
                <lable class="lb2" onclick="command(7)">7</lable>
            </li>
            <li>
                <lable class="lb2" onclick="command(8)">8</lable>
            </li>
            <li>
                <lable class="lb2" onclick="command(9)">9</lable>
            </li>
            <li>
                <lable class="lb3" onclick="yu()">%</lable>
            </li>
            <li>
                <lable class="lb3" onclick="gen()">√</lable>
            </li>
        </ul>
        <ul>
            <li>
                <lable class="lb2" onclick="command(0)">0</lable>
            </li>
            <li>
                <lable class="lb2" onclick="dot()">.</lable>
            </li>
            <li>
                <lable class="lb2" onclick="zhenfu()" value="http://www.mamicode.com/+/-" id="zhenfu">+/-</lable>
            </li>
            <li>
                <lable id="lb4" onclick="clearnum()">c</lable>
            </li>
            <li>
                <lable id="lb6" onclick="equal()">=</lable>
            </li>
        </ul>
    </div>
</div>
//CSS

body {
    margin: 0px;
    padding: 0px;
}

ul {
    margin: 0px;
    padding: 0px;
}

li {
    list-style: none;
    float: left;
}

#maindiv {
    width: 310px;
    height: 400px;
    background: #2C1740;
    margin: 0 auto;
}

#maindiv .lbname {
    display: block;
    margin-left: 30px;
    color: white;
    height: 30px;
    text-align: left;
    line-height: 30px;
}

#content {
    width: 310px;
    height: 100px;
    background: #543382;
    color: white;
    padding-bottom: 0px;
    padding-top: 43px;
    padding-left: 250px;
    box-sizing: border-box;
    font-weight: bold;
}

#num {
    width: 310px;
    height: 20px;
    line-height: 20px;
    background: #543382;
    border: 0;
    color: white;
    margin-left: -250px;
    font-weight: bold;
    padding-left: 250px;
    box-sizing: border-box;
}

#result {
    width: 310px;
    height: 60px;
    cursor: pointer;
}

#result .lb1, #lb5 {
    display: block;
    width: 75px;
    height: 48px;
    line-height: 48px;
    background: #3D568C;
    border: 1px solid black;
    text-align: center;
    font-weight: bold;
    color: white;
}

#result .lb1:hover {
    background-color: lightgray;
}

#result #lb5:hover {
    background-color: lightgray;
}

#other {
    width: 310px;
    height: 230px;
}

#other ul li {
    float: left;
}

#other .lb2 {
    display: block;
    width: 60px;
    height: 50px;
    line-height: 50px;
    background: #717171;
    border: 1px solid black;
    text-align: center;
    cursor: pointer;
    color: white;
    font-weight: bold;
}

#other .lb2:hover {
    background-color: lightgray;

}

#other .lb3, #lb4, #lb6 {
    display: block;
    width: 60px;
    height: 50px;
    line-height: 50px;
    background: #D56503;
    border: 1px solid black;
    text-align: center;
    cursor: pointer;
    color: white;
    font-weight: bold;
}

#other .lb3:hover {
    background-color: lightgray;
}

#other #lb4:hover {
    background-color: lightgray;
}

#other #lb6:hover {
    background-color: lightgray;
}

#note {
    float: left;
    width: 210px;
    height: auto;
    overflow: hidden;
    color: red;
    margin-left: -100px;
    margin-bottom: 20px;
}
js部分

var num = 0, result = 0, numshow = "0";
var operate = 0;//判断输入状态
var calcul = 0;//判断计算状态
var quit = 0;//防止重复按键的标志
var va = document.getElementById("num");//获取输入的值
var ds = document.getElementById("zhenfu");
function command(num) {
    va.value = http://www.mamicode.com/(va.value !="0") ? ((operate == 0) ? va.value : "") : "";//
    va.value = http://www.mamicode.com/va.value + String(num);//给当前字符追加字符
    va.value = http://www.mamicode.com/va.value;//刷新显示
    operate = 0;//重置输入状态
    quit = 0;//防止重复输入状态
}

function dot() {
    va.value = http://www.mamicode.com/(va.value !="0") ? ((operate == 0) ? va.value : "0") : "0";
    for (var i = 0; i <= va.value.length; i++) {
        if (va.value.substr(i, 1) == ".")
            return false;
    }
    va.value = http://www.mamicode.com/va.value +".";
    va.value = http://www.mamicode.com/va.value;
    operate = 0;
}
//清除数据
function clearnum() {
    num = 0;
    result = 0;
    numshow = "0";
    va.value = "http://www.mamicode.com/0";
}
//加法
function plus() {
    calculate();//计算函数
    operate = 1;//更改输入状态
    calcul = 1;//更改计算状态
}
function jian() {
    calculate();//计算函数
    operate = 1;//更改输入状态
    calcul = 2;//更改计算状态
}
function chen() {
    calculate();//计算函数
    operate = 1;//更改输入状态
    calcul = 3;//更改计算状态
}
function chu() {
    calculate();//计算函数
    operate = 1;//更改输入状态
    calcul = 4;//更改计算状态
}
function yu() {
    va.value = http://www.mamicode.com/va.value / 100;
    operate = 1;//更改输入状态
    calcul = 5;//更改计算状态
}
function equal() {
    calculate();//计算函数
    operate = 1;//更改输入状态
    num = 0;
    result = 0;
    numshow = "0";
}
//开根号
function gen() {
    va.value = http://www.mamicode.com/Math.sqrt(va.value);
    operate = 1;
    calcul = 6;
}
//tan值
function tan() {
    va.value = http://www.mamicode.com/Math.tan(va.value);
    operate = 1;
    calcul = 7;
}
//正负运算
function zhenfu() {
    if (ds.innerHTML == "+/-") {
        va.value = http://www.mamicode.com/-1 * va.value;
    }
    operate = 1;
    calcul = 8;
}
function sin() {
    va.value = http://www.mamicode.com/Math.sin(va.value);
    operate = 1;
    calcul = 9;
}
function cos() {
    va.value = http://www.mamicode.com/Math.cos(va.value);
    operate = 1;
    calcul = 10;
}
function calculate() {
    numshow = Number(va.value);
    if (num != 0 && quit != 1) {
        switch (calcul) {
            case 1:
                result = num + numshow;
                break;
            case 2:
                result = num - numshow;
                break;
            case 3:
                result = num * numshow;
                break;
            case 4:
                if (numshow != 0)
                    result = num / numshow;
                else {
                    document.getElementById("note").innerHTML = "除数不能为零！";
                    setTimeout(clearnote, 4000);
                }
                break;
            case  7:
                result = Math.tan(num);
                break;
            case 9:
                result = Math.sin(num);
                break;
            case 10:
                result = Math.cos(num);
                break;
        }
        quit = 1;//防止重复按键
    }
    else {
        result = numshow;
    }
    numshow = String(result);
    va.value = http://www.mamicode.com/numshow;
    num = result;//存储当前值
}
function clearnote() {
    document.getElementById("note").innerHTML = "";
}

js计算器