JavaScript - Calculate Age Base On Birthday

Submitted by razormist on Tuesday, March 19, 2019 - 18:59.

In this tutorial we will create a Calculate Age Base On Birthday using JavaScript. This code will calculate a person age by inputting a person birth date in the textbox. The code itself use a new Date() function to compute the age by getting the difference between the today and the inputted date. This code is free to use, you can modify it as your own, We will be using JavaScript as a server-side scripting language because It allows greater control of your web page behavior than HTML alone. It is embedded in HTML that responsible to allow user to interact with the computer .

Getting started:

First you have to download bootstrap framework, this is the link for the bootstrap that I used for the layout design https://getbootstrap.com/.

The Main Interface

This code contains the interface of the application. To create this just write these block of code inside the text editor and save this as index.html.

<!DOCTYPE html>
<html lang="en">
        <head>
                <meta charset="UTF-8" name="viewport" content="width=device-width, initial-scale=1"/>
                <link rel="stylesheet" type="text/css" href="css/bootstrap.css"/>
        </head>
<body>
        <nav class="navbar navbar-default">
                <div class="contriner-fluid">
                        <a class="navbar-brand" href="https://sourcecodester.com">Sourcecodester</a>
                </div>
        </nav>
        <div class="col-md-3"></div>
        <div class="col-md-6 well">
                <h3 class="text-primary">JavaScript - Calculate Age Base On Birthday</h3>
                <hr style="border-top:1px dotted #ccc;"/>
                <div class="col-md-3"></div>
                <div class="col-md-6">
                        <div class="form-inline">
                                <input type="date" id="birthday"/>
                                <button class="btn btn-primary" onclick="getAge();">Calculate</button>
                                <h2>Your age is: <span id="result" class="text-primary"></span></h2>
                        </div>
                </div>
        </div>
<script src="js/script.js"></script>    
</body> 
</html>

Creating the Script

This code contains the script of the application. This code will calculate a person age automatically. To do this just copy and write these block of codes inside the text editor, then save it as script.js inside the js folder.

function getAge() {
        var date = document.getElementById('birthday').value;
        
        if(date === ""){
                alert("Please complete the required field!");
    }else{
                var today = new Date();
                var birthday = new Date(date);
                var year = 0;
                if (today.getMonth() < birthday.getMonth()) {
                        year = 1;
                } else if ((today.getMonth() == birthday.getMonth()) && today.getDate() < birthday.getDate()) {
                        year = 1;
                }
                var age = today.getFullYear() - birthday.getFullYear() - year;
                
                if(age < 0){
                        age = 0;
                }
                document.getElementById('result').innerHTML = age;
        }
}

There you have it we successfully created a Calculate Age Base On Birthday using JavaScript. I hope that this simple tutorial help you to what you are looking for. For more updates and tutorials just kindly visit this site. Enjoy Coding!

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