Calculator Using HTML,CSS & JavaScript With Source Code

Welcome to Code With Random blog. This blog teaches us how to create a Calculator Using Html, Css, and JavaScript Code. We use HTML to create the Layout Of the Calculator and use Css for the Styling Calculator and Use JavaScript for the Calculation in our calculator project.

I hope you enjoy our blog so let's start with a basic HTML structure for the Calculator.

HTML Code For Calculator

<div class="calculator">
  <div class="input" id="input"></div>
  <div class="buttons">
    <div class="operators">
      <div>+</div>
      <div>-</div>
      <div>&times;</div>
      <div>&divide;</div>
    </div>
    <div class="leftPanel">
      <div class="numbers">
        <div>7</div>
        <div>8</div>
        <div>9</div>
      </div>
      <div class="numbers">
        <div>4</div>
        <div>5</div>
        <div>6</div>
      </div>
      <div class="numbers">
        <div>1</div>
        <div>2</div>
        <div>3</div>
      </div>
      <div class="numbers">
        <div>0</div>
        <div>.</div>
        <div id="clear">C</div>
      </div>
    </div>
    <div class="equal" id="result">=</div>
  </div>
</div>

There is all the HTML Code for the Calculator Project. Now, you can see output without Css and JavaScript. Then we write Css and JavaScript for the Calculator Project.

CSS Code For Calculator

body {
  width: 500px;
  margin: 4% auto;
  font-family: 'Source Sans Pro', sans-serif;
  letter-spacing: 5px;
  font-size: 1.8rem;
  -moz-user-select: none;
  -webkit-user-select: none;
  -ms-user-select: none;
}

.calculator {
  padding: 20px;
  -webkit-box-shadow: 0px 1px 4px 0px rgba(0, 0, 0, 0.2);
  box-shadow: 0px 1px 4px 0px rgba(0, 0, 0, 0.2);
  border-radius: 1px;
}

.input {
  border: 1px solid #ddd;
  border-radius: 1px;
  height: 60px;
  padding-right: 15px;
  padding-top: 10px;
  text-align: right;
  margin-right: 6px;
  font-size: 2.5rem;
  overflow-x: auto;
  transition: all .2s ease-in-out;
}

.input:hover {
  border: 1px solid #bbb;
  -webkit-box-shadow: inset 0px 1px 4px 0px rgba(0, 0, 0, 0.2);
  box-shadow: inset 0px 1px 4px 0px rgba(0, 0, 0, 0.2);
}

.buttons {}

.operators {}

.operators div {
  display: inline-block;
  border: 1px solid #bbb;
  border-radius: 1px;
  width: 80px;
  text-align: center;
  padding: 10px;
  margin: 20px 4px 10px 0;
  cursor: pointer;
  background-color: #ddd;
  transition: border-color .2s ease-in-out, background-color .2s, box-shadow .2s;
}

.operators div:hover {
  background-color: #ddd;
  -webkit-box-shadow: 0px 1px 4px 0px rgba(0, 0, 0, 0.2);
  box-shadow: 0px 1px 4px 0px rgba(0, 0, 0, 0.2);
  border-color: #aaa;
}

.operators div:active {
  font-weight: bold;
}

.leftPanel {
  display: inline-block;
}

.numbers div {
  display: inline-block;
  border: 1px solid #ddd;
  border-radius: 1px;
  width: 80px;
  text-align: center;
  padding: 10px;
  margin: 10px 4px 10px 0;
  cursor: pointer;
  background-color: #f9f9f9;
  transition: border-color .2s ease-in-out, background-color .2s, box-shadow .2s;
}

.numbers div:hover {
  background-color: #f1f1f1;
  -webkit-box-shadow: 0px 1px 4px 0px rgba(0, 0, 0, 0.2);
  box-shadow: 0px 1px 4px 0px rgba(0, 0, 0, 0.2);
  border-color: #bbb;
}

.numbers div:active {
  font-weight: bold;
}

div.equal {
  display: inline-block;
  border: 1px solid #3079ED;
  border-radius: 1px;
  width: 17%;
  text-align: center;
  padding: 127px 10px;
  margin: 10px 6px 10px 0;
  vertical-align: top;
  cursor: pointer;
  color: #FFF;
  background-color: #4d90fe;
  transition: all .2s ease-in-out;
}

div.equal:hover {
  background-color: #307CF9;
  -webkit-box-shadow: 0px 1px 4px 0px rgba(0, 0, 0, 0.2);
  box-shadow: 0px 1px 4px 0px rgba(0, 0, 0, 0.2);
  border-color: #1857BB;
}

div.equal:active {
  font-weight: bold;
}

JavaScript Code For Calculator

"use strict";

var input = document.getElementById('input'), // input/output button
  number = document.querySelectorAll('.numbers div'), // number buttons
  operator = document.querySelectorAll('.operators div'), // operator buttons
  result = document.getElementById('result'), // equal button
  clear = document.getElementById('clear'), // clear button
  resultDisplayed = false; // flag to keep an eye on what output is displayed

// adding click handlers to number buttons
for (var i = 0; i < number.length; i++) {
  number[i].addEventListener("click", function(e) {

    // storing current input string and its last character in variables - used later
    var currentString = input.innerHTML;
    var lastChar = currentString[currentString.length - 1];

    // if result is not diplayed, just keep adding
    if (resultDisplayed === false) {
      input.innerHTML += e.target.innerHTML;
    } else if (resultDisplayed === true && lastChar === "+" || lastChar === "-" || lastChar === "×" || lastChar === "÷") {
      // if result is currently displayed and user pressed an operator
      // we need to keep on adding to the string for next operation
      resultDisplayed = false;
      input.innerHTML += e.target.innerHTML;
    } else {
      // if result is currently displayed and user pressed a number
      // we need clear the input string and add the new input to start the new opration
      resultDisplayed = false;
      input.innerHTML = "";
      input.innerHTML += e.target.innerHTML;
    }

  });
}

// adding click handlers to number buttons
for (var i = 0; i < operator.length; i++) {
  operator[i].addEventListener("click", function(e) {

    // storing current input string and its last character in variables - used later
    var currentString = input.innerHTML;
    var lastChar = currentString[currentString.length - 1];

    // if last character entered is an operator, replace it with the currently pressed one
    if (lastChar === "+" || lastChar === "-" || lastChar === "×" || lastChar === "÷") {
      var newString = currentString.substring(0, currentString.length - 1) + e.target.innerHTML;
      input.innerHTML = newString;
    } else if (currentString.length == 0) {
      // if first key pressed is an opearator, don't do anything
      console.log("enter a number first");
    } else {
      // else just add the operator pressed to the input
      input.innerHTML += e.target.innerHTML;
    }

  });
}

// on click of 'equal' button
result.addEventListener("click", function() {

  // this is the string that we will be processing eg. -10+26+33-56*34/23
  var inputString = input.innerHTML;

  // forming an array of numbers. eg for above string it will be: numbers = ["10", "26", "33", "56", "34", "23"]
  var numbers = inputString.split(/\+|\-|\×|\÷/g);

  // forming an array of operators. for above string it will be: operators = ["+", "+", "-", "*", "/"]
  // first we replace all the numbers and dot with empty string and then split
  var operators = inputString.replace(/[0-9]|\./g, "").split("");

  console.log(inputString);
  console.log(operators);
  console.log(numbers);
  console.log("----------------------------");

  // now we are looping through the array and doing one operation at a time.
  // first divide, then multiply, then subtraction and then addition
  // as we move we are alterning the original numbers and operators array
  // the final element remaining in the array will be the output

  var divide = operators.indexOf("÷");
  while (divide != -1) {
    numbers.splice(divide, 2, numbers[divide] / numbers[divide + 1]);
    operators.splice(divide, 1);
    divide = operators.indexOf("÷");
  }

  var multiply = operators.indexOf("×");
  while (multiply != -1) {
    numbers.splice(multiply, 2, numbers[multiply] * numbers[multiply + 1]);
    operators.splice(multiply, 1);
    multiply = operators.indexOf("×");
  }

  var subtract = operators.indexOf("-");
  while (subtract != -1) {
    numbers.splice(subtract, 2, numbers[subtract] - numbers[subtract + 1]);
    operators.splice(subtract, 1);
    subtract = operators.indexOf("-");
  }

  var add = operators.indexOf("+");
  while (add != -1) {
    // using parseFloat is necessary, otherwise it will result in string concatenation :)
    numbers.splice(add, 2, parseFloat(numbers[add]) + parseFloat(numbers[add + 1]));
    operators.splice(add, 1);
    add = operators.indexOf("+");
  }

  input.innerHTML = numbers[0]; // displaying the output

  resultDisplayed = true; // turning flag if result is displayed
});

// clearing the input on press of clear
clear.addEventListener("click", function() {
  input.innerHTML = "";
})

Now that we have completed our Calculator. our updated output with Html, Css, and JavaScript. Hope you like the Calculator Project. you can see the output video and project screenshots. See our other blogs and gain knowledge in front-end development.

Thank you!

This post teaches us how to create a Calculator Using HTML, CSS, And JavaScript. If we made a mistake or any confusion, please drop a comment to reply or help you in easy learning.

Written by - Code With Random/Anki

Code By - Vikas Lalwani