Untitled

<HTML>
<HEAD>
<TITLE>Exemple 1</TITLE>
</HEAD>
<BODY>
<form>
    <center>
        First Name:<input type="text" name="fname" id="Fname">
        Last Name:<input type="text" name="lname" id="Lname">
        Age:<input type="text" name="age" id="age">
        <button onclick="myFunction()">Submit</button>
    </center>
    </form>
<script>
    function myFunction(){
        var first = document.getElementById("Fname").value;
        var last = document.getElementById("Lname").value;
        var age =  document.getElementById("age").value;
        if(age>0 && age<18){
            alert(first+" "+last+". Tu as "+age+" et tu est un mineur");
        }
        else{
            alert(first+" "+last+". Tu as "+age+" et tu est un adulte");
        }

    }
    </script>
</BODY>
</HTML>