Pizza Formalvalidierung JQuery

<html>
    <head>
        <title>HTML and Java Script</title>
        <meta charset="UTF-8">
        <meta name="viewport" content="width=device-width, initial-scale=1.0">
        <script type="text/javascript">
            function validate(){
                if( document.PizzaForm.customer.value == "" ) {
                     alert( "Please provide name" );
                     document.PizzaForm.customer.focus() ;
                     return false;
                 }
                 if( document.PizzaForm.address.value == "" ) {
                     alert( "Please provide address" );
                     document.PizzaForm.address.focus() ;
                     return false;
                 }
                 if( document.PizzaForm.city.value == "" ) {
                     alert( "Please provide city" );
                     document.PizzaForm.city.focus() ;
                     return false;
                 }
                 if( document.PizzaForm.state.value == "" ) {
                     alert( "Please provide state" );
                     document.PizzaForm.state.focus() ;
                     return false;
                 }
                 if( document.PizzaForm.zip.value == "" ) {
                     alert( "Please provide zip" );
                     document.PizzaForm.zip.focus() ;
                     return false;
                 }
                 if( document.PizzaForm.zip.value == "" || isNaN( document.PizzaForm.zip.value ) ||
                     document.PizzaForm.zip.value.length != 5 ) {
                     alert( "Please provide a zip in 5 digit number format" );
                     document.PizzaForm.zip.focus() ;
                     return false;
                 }
                 
                 if( document.PizzaForm.phone.value == "" ) {
                     alert( "Please provide phone" );
                     document.PizzaForm.phone.focus() ;
                     return false;
                 }
                 var phone=document.PizzaForm.phone.value;  
                if (isNaN(phone)){  
                    alert("Enter Numeric value only");  
                    return false;  
                }
                if(phone.length!=10){  
                    alert("Phone number must be 10 numbers long");  
                    return false;  
                }  
                 
                //radio button validation
                var size = document.PizzaForm.sizes;
                for (var i=0; i<size.length; i++) {
                if (size[i].checked)
                    break;
                }
                if (i===size.length)
                    return alert("No radio button is checked");
                   // alert("Radio Button " + (i+1) + " is checked");
                                
                //checkbox validation
                var toppings = document.PizzaForm.toppings;
                for (var i=0; i<toppings.length; i++) {
                if (toppings[i].checked)
                    break;
                }
                if (i==toppings.length)
                    return alert("No Checkbox is checked");
                   // alert("check box " + (i+1) + " is checked.");
            }
            
        </script>
    </head>
    <body>
        <form name="PizzaForm">
            <h1>The Java Script Pizza Parlor</h1>
            <p>
            <h4>Step 1: Enter Your name,address,and phone number:</h4>
            <font face="Courier New">
            Name: &nbsp;&nbsp;&nbsp;<input name="customer" size="50" type="text"><br>
            Address: <input name="address" size="50" type="text"><br>
            City: &nbsp;&nbsp;&nbsp;<input name="city" size="15" type="text">
            State: <input name="state" size="2" type="text">
            Zip: <input name="zip" size="5" type="text"><br>
            Phone: &nbsp;&nbsp;<input name="phone" size="50" type="text"><br>
            </font>
            </p>
            <p>
            <h4>Step 2: Select the size of pizza you want:</h4>
            <font face="Courier New">
            <input name="sizes" type="radio">Small
            <input name="sizes" type="radio">Medium
            <input name="sizes" type="radio">Large<br>
            </font>
            </p>
            <p>
            <h4>Step 3: Select the Pizza toppings you want:</h4>
             <font face="Courier New">
            <input name="toppings" type="checkbox">Pepperoni
            <input name="toppings" type="checkbox">Canadian Bacon
            <input name="toppings" type="checkbox">Sausage<br>
            <input name="toppings" type="checkbox">Mushrooms
            <input name="toppings" type="checkbox">Pineapple
            <input name="toppings" type="checkbox">Black Olives<br>
            </font>
            </p>
            <input type="button" value="Submit Order" onclick="return validate()">
            <input type="button" value="Clear Entries" >
        </form>
    </body>
</html>
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