Calculator

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10 January 2025

<!DOCTYPE html>
<html lang="en" >
<head>
  <meta charset="UTF-8">
  <title>Andev Web</title>
  <link rel='stylesheet' href='https://fonts.googleapis.com/css2?family=Open+Sans:wght@600&family=Press+Start+2P&display=swap'><link rel="stylesheet" href="./style.css">

</head>
<body>
<div class="calculator">
  <div class="screen-wrapper">
    <div id="screen">
      <div id="expression"><span id="typed-cursor"/></div>
      <div id="result">0</div>
    </div>
  </div>
  <table class="keys">
    <tbody>
      <tr>
        <td class="red key" data-func="clear">C</td>
        <td class="red key" data-func="cancel_entry">CE</td>
        <td class="gray key power" data-token="op_pow">x<span>y</span></td>
        <td class="gray key divide" data-token="op_divide">÷</td>
      </tr>
      <tr>
        <td class="blue key" data-token="num_7">7</td>
        <td class="blue key" data-token="num_8">8</td>
        <td class="blue key" data-token="num_9">9</td>
        <td class="gray key" data-token="op_multiply">×</td>
      </tr>
      <tr>
        <td class="blue key" data-token="num_4">4</td>
        <td class="blue key" data-token="num_5">5</td>
        <td class="blue key" data-token="num_6">6</td>
        <td class="gray key substract" data-token="op_substract">–</td>
      </tr>
      <tr>
        <td class="blue key" data-token="num_1">1</td>
        <td class="blue key" data-token="num_2">2</td>
        <td class="blue key" data-token="num_3">3</td>
        <td class="gray key add" data-token="op_add" rowspan="2">+</td>
      </tr>
      <tr>
        <td class="blue key" data-token="num_dot">.</td>
        <td class="blue key" data-token="num_0">0</td>
        <td class="blue key eval" data-func="eval">=</td>
      </tr>
    </tbody>
  </table>
  <p class="footer">Andev Web</p>
</div>
  <script  src="./script.js"></script>

</body>
</html>

CSS

html {
  width: 100%;
  height: 100%;
  padding: 0;
  margin: 0;
  display: flex;
  align-items: center;
  justify-content: center;
}

body {
  padding: 0;
  margin: 0;
  background-image: linear-gradient(to right, #bdc3c7 0%, #ecf0f1 40%, #ecf0f1 60%, #bdc3c7 100%);
}

.calculator {
  width: 250px;
  background-color: #2c3e50;
  background-image: linear-gradient(to right, #334b63 0%, #4b6580 40%, #4b6580 60%, #334b63 100%);
  border-width: 1px;
  border-style: solid;
  border-top-color: rgba(255, 255, 255, 0.6);
  border-bottom-color: black;
  border-right-color: black;
  border-left-color: black;
  border-radius: 8px;
  box-shadow: 0 0 10px rgba(0, 0, 0, 0.4), inset 0 0 3px 4px rgba(0, 0, 0, 0.5);
  border-top: 4px solid rgba(255, 255, 255, 0.2);
}

/* Screen
-------------------------------*/
.screen-wrapper {
  margin: 15px;
  padding: 3px;
  background-color: rgba(0, 0, 0, 0.3);
  box-shadow: 0 2px 2px rgba(255, 255, 255, 0.5);
  border-radius: 5px;
}

#screen {
  height: 60px;
  background-image: linear-gradient(to bottom, #ffcc00 0%, #ffde74 100%);
  border-radius: 30%/7%;
  box-shadow: inset 0 0 20px rgba(0, 0, 0, 0.6);
  padding: 8px 5px;
}

#expression {
  font-family: "Press Start 2P", cursive;
  font-size: 12px;
  height: 20px;
  line-height: 20px;
  overflow: hidden;
  white-space: nowrap;
  display: flex;
  align-items: center;
}
#result {
  font-family: "Press Start 2P", cursive;
  font-size: 28px;
  text-align: right;
  margin-top: 10px;
  white-space: nowrap;
}
#typed-cursor {
  border-right: 3px solid black;
  height: 14px;
  animation: 1s blink step-end infinite;
}

@keyframes blink {
  from, to {
    border-color: transparent;
  }
  50% {
    border-color: black;
  }
}
.keys {
  width: 100%;
  border-spacing: 12px;
}

.key {
  width: 25%;
  cursor: pointer;
  font-family: "Open Sans", sans-serif;
  color: #ecf0f1;
  font-size: 18px;
  text-align: center;
  padding: 8px 0;
  border-radius: 5px;
  border-width: 3px;
  border-style: solid;
  border-top-color: rgba(255, 255, 255, 0.2);
  border-left-color: rgba(0, 0, 0, 0.1);
  border-right-color: rgba(0, 0, 0, 0.1);
  border-bottom-color: rgba(0, 0, 0, 0.3);
  box-shadow: 0 0 4px 2px rgba(0, 0, 0, 0.7);
  transition: all 0.2s ease-out;
}
.key:hover {
  border: 3px solid rgba(226, 154, 26, 0.6);
  box-shadow: 0 0 4px 2px rgba(0, 0, 0, 0.7), inset 0 0 6px rgba(0, 0, 0, 0.4);
  color: #e2aa1a;
  text-shadow: 0 0 10px #ffda99;
}
.key.red {
  background-image: linear-gradient(to bottom, #963434 0%, #be4d4d 50%, #963434 100%);
}
.key.blue {
  background-image: linear-gradient(to bottom, #2c3e50 0%, #3a5066 50%, #2c3e50 100%);
}
.key.gray {
  background-image: linear-gradient(to bottom, #6e8597 0%, #829baf 50%, #6e8597 100%);
}
.key.substract, .key.divide, .key.add, .key.eval {
  font-size: 28px;
  line-height: 18px;
}
.key.substract {
  vertical-align: top;
}
.key span {
  font-size: 10px;
  vertical-align: top;
}

.footer {
  font-family: "Open Sans", sans-serif;
  font-size: 12px;
  text-align: center;
  color: rgba(0, 0, 0, 0.5);
  text-shadow: 0 1px 0 rgba(255, 255, 255, 0.17);
}

JS

window.onload = function() {
    new Calculator();
};

/**
 * Calculator class
 */
function Calculator() {
    this.op_add       = '+';
    this.op_substract = '-';
    this.op_multiply  = '*';
    this.op_divide    = '/';
    this.op_pow       = '^';

this.num_1   = 1;
    this.num_2   = 2;
    this.num_3   = 3;
    this.num_4   = 4;
    this.num_5   = 5;
    this.num_6   = 6;
    this.num_7   = 7;
    this.num_8   = 8;
    this.num_9   = 9;
    this.num_0   = 0;
    this.num_dot = '.';
    
    this.screen = new Screen(this);
    this.keys = new Keyboard(this);
}

Calculator.prototype.infixToPostfix = function( infix ) {
    var length = infix.length;
    var stack = new Array(); // Holds operators
    var postfix = ""; // The result expression
    var chars = infix.split('');

// Each character
    for ( var i = 0; i < length; i++ ) {
        var curChar = chars[i],
            nextChar = '';

// Get the next char (unless it's the last char)
        if(i < length-1) {
            nextChar = chars[i+1];
        }

// Operators
        if(!this.isInt(chars[i]) && chars[i] !== ".") {
            
            while ( stack.length > 0 ) {
                if (this.comparePrecedence(stack.peek(), curChar)) {
                    postfix += stack.pop() + " ";
                }
                else {
                    break;
                }
            }
            stack.push(curChar);
        }

// Operands
        else {
            if(this.isInt(nextChar) || nextChar === '.')
                postfix += curChar;
            else postfix += curChar + " ";
        }
    }

// Pop the remaining operators
    while (stack.length > 0) {
        postfix += stack.pop() + " ";
    }

return postfix.trim();
};

Calculator.prototype.postfixEval = function( postfix ) {
    var resultStack = new Array();
    var postfix = postfix.split(" ");
    var length = postfix.length;
    var decimal;
    var curElement;

// Each element
    for ( var i = 0; i < length; i++ ) {
        curElement = postfix[i];

// Operand
        if( this.isFloat(curElement) ) {
            var decimal = parseFloat(curElement);
            resultStack.push(decimal);
        }

// Operator
        else {
            var result = this.applyOperator(resultStack.pop(), resultStack.pop(), curElement);
            resultStack.push(result);
        }	
    }
    return resultStack.pop();
};

Calculator.prototype.comparePrecedence = function( op_a, op_b ) {
    var precedence = ['+','-','*','/','^','(',')'];
    return precedence.indexOf(op_a) > precedence.indexOf(op_b);
};

Calculator.prototype.applyOperator = function(b, a, operator) {
    switch( operator ) {
        case "+":
            return a + b;
        case "-":
            return a - b;
        case "*":
            return a * b;
        case "/":
            return a / b;
        case "^":
            return Math.pow(a, b);
    }
}

Calculator.prototype.isInt = function( num ) {
    return !isNaN(parseInt(num));
};

Calculator.prototype.isFloat = function( num ) {
    return !isNaN(parseFloat(num));
};

/**
 * Screen class
 */
function Screen( calculator ) {
    this.calculator = calculator;
    this.expressionHolder = document.getElementById('expression');
    this.expression = '';
    this.result = document.getElementById('result');
    this.cursor = new Cursor(this);
}

Screen.prototype.appendToExpression = function( token ) {
    var value = this.calculator[token];
    this.expressionHolder.innerHTML += value;
    this.expressionHolder.scrollLeft = this.expressionHolder.scrollWidth;
    this.expression += value;
    this.cursor.moveToEnd();
};

Screen.prototype.setResult = function( number ) {
    this.result.innerHTML = number.toString().slice(0,11);
    this.expression = number.toString();
    this.expressionHolder.innerHTML = number;
    this.cursor.moveToEnd();
};

Screen.prototype.clear = function() {
    this.result.innerHTML = 0;
    this.expressionHolder.innerHTML = '';
    this.expression = '';
    this.cursor.moveToStart();
};

Screen.prototype.cancelEntry = function() {
    this.expressionHolder.innerHTML = '';
    this.expression = '';
    this.cursor.moveToStart();
};

/**
 * Cursor class
 */
function Cursor( screen ) {
    this.screen = screen;
    this.pos = 0;
}

Cursor.prototype.moveTo = function( pos ) {
    if( pos >= 0 && pos <= this.screen.expression.length) {
        // Remove current cursor
        try {
            document.getElementById('expression').removeChild(document.getElementById('typed-cursor'));
        }
        catch(e) {

}
      
        // Recreate it
        var cursor = '<span id="typed-cursor"></span>';
        var expression = this.screen.expression;
        expression = expression.substring(0,pos) + cursor + expression.substring(pos, expression.length);
        this.pos = pos;
        document.getElementById('expression').innerHTML = expression;
    }
};

Cursor.prototype.moveToEnd = function() {
    this.moveTo(this.screen.expression.length);
};

Cursor.prototype.moveToStart = function() {
    this.moveTo(0);
};

/**
 * Keyboard class
 */
function Keyboard( calculator ) {
    this.calculator = calculator;
    this.keys = document.querySelectorAll('.key');
    for( var i = 0; i < this.keys.length; i++ ) {
        var self = this;
        this.keys[i].onclick = function() {
            self.keyPress(this);
        };
    }
}

Keyboard.prototype.keyPress = function( key ) {
    if( key.getAttribute("data-func") === null) {
        this.calculator.screen.appendToExpression( key.getAttribute("data-token") );
    }
    else {
        this['key_' + key.getAttribute("data-func")]();
    }
};

// Calculator key actions

Keyboard.prototype.key_eval = function() {
    var postfix = this.calculator.infixToPostfix(this.calculator.screen.expression);
    this.calculator.screen.setResult(this.calculator.postfixEval(postfix));
};

Keyboard.prototype.key_clear = function() {
    this.calculator.screen.clear();
};

Keyboard.prototype.key_cancel_entry = function() {
    this.calculator.screen.cancelEntry();
};

Array.prototype.peek = function() {
    return this[this.length-1];
};

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