nice.js

// Defining a function to display error message
function printError(elemId, hintMsg) {
    document.getElementById(elemId).innerHTML = hintMsg;
}

// Defining a function to validate form
function validateForm() {
    // Retrieving the values of form elements
    var name = document.contactForm.name.value;
    var number = document.contactForm.number.value;
    var date = document.contactForm.date.value;


	// Defining error variables with a default value
    var nameErr = numberErr = dateErr = true;


    if(name == "") {
        printError("nameErr", "Please enter your name");
    } else {
        printError("nameErr", "");
        nameErr = false;
    }


    if(number == "") {
        printError("numberErr", "Please enter your number");
    } else {
        if(!(number >>> 0 === parseFloat(number))) {
            printError("numberErr", "Please enter a positive integer");
        } else{
            printError("numberErr", "");
            numberErr = false;
        }
    }

    if(date == "") {
        printError("dateErr", "Please enter your date number");
    } else {
		var dateEntered = Date.parse(date);
        if(isNaN(dateEntered)) {
            printError("dateErr", "Please enter a valid date");
        } else{
            printError("dateErr", "");
            dateErr = false;
        }
    }

	$(document).ready(function(){
	  $("button").click(function(){
		$("p").text("Hello world!");
		$(this).css({ 'color': 'red', 'font-size': '150%' });
		//$( ".row" ).remove();
		$( ".row" ).append( "<p>Test</p>" );
	  });
	});

    if((nameErr || numberErr || dateErr) == true) {
       return false;
    } else {
        var dataPreview = "You've entered the following details: \n" +
                          "Name: " + name + "\n" +
                          "number: " + number + "\n" +
                          "date: " + date + "\n";
        alert(dataPreview);
    }
};