how to validate a form using JavaScript? [closed]

Answer 1

If you are using jQuery (if not, you should) you can do something when the form gets submitted through .submit(). Within this event you can check all the input fields depending on their type, if an error occurs you can call event.preventDefault() to stop the submitting and alert() an error.

Something like this:

<form id="myform">
    <input type="text" name="text" />
    <input type="submit" value="Submit!" />
</form>

jQuery:

$('#myform').submit(function(event){

    error = false;

    $('input',this).each(function(){

        if($(this).val() == '')
            error = true;

    });

    if(error == true){

        event.preventDefault();
        alert('An error occured!');

    }

});

Answer 2

Call a JavaScript function which validates user input fields using the forms onSubmit method.

Answer 3

add an OnClick="function_name();" in the html of your submit button,

and in the declaration of the function do this

function function_name(){
     var str = document.getElement("your_text_field_id");
     if (str=="") {
       alert("Please type some text first");
       return false
     } else { 
       alert("Thanks");  //optional
       return true;
     }
}