What is JavaScript :

JavaScript is the Programming Language for the Web.
JavaScript can update and change both HTML and CSS.
JavaScript can calculate, manipulate and validate data.

Function to perform operation

Function	Operation
add()	Addition Of Two Numbers
sub()	Substraction Of Two Numbers
mul()	Multiplication Of Two Numbers
div()	Division Of Two Numbers

Tools and technologies used

• HTML
• CSS
• JavaScript
• Notepad++

Code Details

Script to perform operations

<script type="text/javascript">
    /* Functions to get the value main purpose to reduce redundancy*/
    function getValue(firstNumber, secondNumber){
        x = document.getElementById("firstNumber").value;
        y = document.getElementById("secondNumber").value;
    }
    /*Function to add two numbers*/
    function add() {
        /* Get the value to add numbers*/
        getValue();
        /*The Number() function converts the object argument to a number
          that represents the object's value*/
        sum=Number(x)+Number(y);
        /*print the number after addition*/
        document.getElementById("result").innerHTML =  x+" + "+y+" = "+sum;
    }
    /*Function to subtract two numbers*/
    function sub() {
        /* Get the value to subtract numbers*/
        getValue();
        /*The Number() function converts the object argument to a number
          that represents the object's value*/
        sub=Number(x)-Number(y);
        /*print the number after subtraction*/
        document.getElementById("result").innerHTML = x+" - "+y+" = "+sub;
    }
    /*Function to multiply two numbers*/
    function mul() {
        /* Get the value to multiply numbers*/
        getValue();
        /*The Number() function converts the object argument to a number
          that represents the object's value*/
        mul=Number(x)*Number(y);
        /*print the number after multiplication*/
        document.getElementById("result").innerHTML = x+" * "+y+" = "+mul;
    }
    /*Function to divide two numbers*/
    function div() {
        /* Get the value to divide numbers*/
        getValue();
        /*The Number() function converts the object argument to a number
          that represents the object's value*/
        div=Number(x)/Number(y);
        /*print the number after division*/
        document.getElementById("result").innerHTML = x+" / "+y+" = "+div;
    }
</script>

HTML code to get input

<table>
  <h1>Online Calculator</h1>
  <tr>
    <td>Enter a first number : </td>
    <!--Get first input-->
    <td><input type="text" id="firstNumber"  required /></td>
  </tr>
  <tr>
    <!--Get second input-->
    <td>Enter a second number : </td>
    <td><input type="text" id="secondNumber" required /></td>
  </tr>
</table>
<br/>
<!--Function for Addition-->
<button onclick="add()">Add</button>
<!--Function for Substraction-->
<button onclick="sub()">Substract</button>
<!--Function for Multiplication-->
<button onclick="mul()">Multiply</button>
<!--Function for Division-->
<button onclick="div()">Divide</button><br/>
<!--For showing result-->
<p id="result">Result</p>

Output

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