Калькулятор

Простой калькулятор на JavaScript

by alex_xpert

HTML

<!DOCTYPE html>
<html>
    <head>
        <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
    </head>
    <body>
        <div id="calculator">
            <table>
                <tr>
                    <td colspan="4"><div id="display"></div></td>
                </tr>
                <tr>
                    <td><button onclick="prnt(1)">1</button></td>
                    <td><button onclick="prnt(2)">2</button></td>
                    <td><button onclick="prnt(3)">3</button></td>
                    <td><button onclick="calc('addition')">+</button></td>
                </tr>
                <tr>
                    <td><button onclick="prnt(4)">4</button></td>
                    <td><button onclick="prnt(5)">5</button></td>
                    <td><button onclick="prnt(6)">6</button></td>
                    <td><button onclick="calc('subtraction')">-</button></td>
                </tr>
                <tr>
                    <td><button onclick="prnt(7)">7</button></td>
                    <td><button onclick="prnt(8)">8</button></td>
                    <td><button onclick="prnt(9)">9</button></td>
                    <td><button onclick="calc('multiplication')">*</button></td>
                </tr>
                <tr>
                    <td><button onclick="prnt(0)">0</button></td>
                    <td><button onclick="prnt('.')">.</button></td>
                    <td><button onclick="result()">=</button></td>
                    <td><button onclick="calc('division')">/</button></td>
                </tr>
                <tr>
                <td colspan="4"><button onclick="reset()">Сброс</button></td>
                </tr>
            </table>
        </div>
    </body>
</html>

CSS

#calculator {
    width:145px;
    height: 170px;
    position: absolute;
    top: 50%;
    left: 50%;
    margin-left: -75px;
    margin-top: -125px;
    text-align: center;
    border: 1px solid #C0C0C0;
    padding: 5px;
}

#display {
    width: 138px;
    height: 20px;
    background-color: #F5F5F5;
    border: 1px solid #C0C0C0;
    text-align: right;
}

JavaScript

var operand = null;
var operation = null;

function prnt(c) {
    document.getElementById("display").innerHTML = document.getElementById("display").innerHTML + c;
}

function calc(o) {
    operand = document.getElementById("display").innerHTML;
    operation = o;
    document.getElementById("display").innerHTML = "";
}

function result() {
    if (operand === null || operation === null || document.getElementById("display").innerHTML === "") {
        alert("Нечего считать!");
        return;
    }
    other_operand = document.getElementById("display").innerHTML - 0;
    r = 0;
    switch (operation) {
    case "addition":
        r = +operand + other_operand;
        break;
    case "subtraction":
        r = operand - other_operand;
        break;
    case "multiplication":
        r = operand * other_operand;
        break;
    case "division":
        r = operand / other_operand;
        break;
    }
    document.getElementById("display").innerHTML = r;
}

function reset() {
    document.getElementById("display").innerHTML = "";
    operand = null;
    operation = null;
}