JSFiddle - React, Tailwind, and code Playground

HTML

<script src="http://coffeeonmars.com/W150/assignments/asst_09/js/jquery-2.0.3.min.js"></script>
	<form id="userInfo-form" action="success.html">
		<p>
			<label>First Name:
				<input type="text" id="first-name" name="first-name">
			</label>
			<span id="error-first-name" class="hidden error">* Must be at least 6 characters
		</p>
		
		<p>
			<label>Last Name:
				<input type="text" id="last-name" name="last-name">
			</label>
			<span id="error-last-name" class="hidden error">* Must be at least 6 characters
		</p>
		
		<p>
			<label>Age:
				<input type="number" id="age" name="age">
			</label>
			<span id="error-age" class="hidden error">* Not a number >=0
		</p>
		
		<button type="submit" name="submit">Continue</button>
	</form>

CSS

.error{
			color:red;
		}
		.hidden {
			display:none;	
		}

JavaScript

$(document).ready(function(){
    		$("#userInfo-form").submit(validateForm);
    	});
    
    	function validateForm()
    	{
    		$(".error").hide();
    		
    		var validFirstName = 
    			validateTextField("#first-name","#error-first-name");
    			
    		var validLastName = 
    			validateTextField("#last-name","#error-last-name");
    			
    		var validAge = 
    			validateTextField("#age","#error-age");
    			
    		return validFirstName && validLastName && validAge;
    	}
    	
    	function validateTextField(fieldId, errorId)
    	{
    		if($(fieldId).val() == "")
    		{
    			$(errorId).show();
    			return false;
    		}
    	}