validar datos con javascript

esta pequeño codigo javascript, nos muestra como validar los datos con javascript.

Código Javascript


<html>
<head>
<title>validar datos con javascript</title>
<script type="text/javascript">
<!--
function runTest(form, button)  {
	Ret = false;
	if (button.name == "1") Ret = testBox1(form);
	if (button.name == "2") Ret = testBox2(form);
	if (button.name == "3") Ret = testBox3(form);
	if (button.name == "4") Ret = testBox4(form);
	if (Ret)
		alert ("Los datos ingresado son Correctos!");
}

function testBox1(form) {
	Ctrl = form.inputbox1;
	if (Ctrl.value == "" || Ctrl.value.indexOf ('@', 0) == -1) {
              	validatePrompt (Ctrl, "Debes ingresar un e-mail válido")
		return (false);
	} else
		return (true);
}
function testBox2(form) {
	Ctrl = form.inputbox2;
	if (Ctrl.value.length != 5) {
		validatePrompt (Ctrl, "Debes escribir CINCO caracteres")
		return (false);
	} else
		return (true);
}
function testBox3(form) {
         Ctrl = form.inputbox3;
	if (Ctrl.value.length < 3) {
		validatePrompt (Ctrl, "Entrar 3 o mas caracteres")
		return (false);
	} else
		return (true);
}
function testBox4(form) {
	Ctrl = form.inputbox4;
	if (Ctrl.value == "") {
		validatePrompt (Ctrl, "Este campo no puede estar vacio")
		return (false);
	} else
		return (true);
}
function runSubmit (form, button)  {
	if (!testBox1(form)) return;
	if (!testBox2(form)) return;
	if (!testBox3(form)) return;
	if (!testBox4(form)) return;
	alert ("Todas la entradas OK!");
	document.test.submit();	// un-comment to submit form
	return;
}

function validatePrompt (Ctrl, PromptStr) {
	alert (PromptStr)
	Ctrl.focus();
	return;
}

function loadDoc() {

	// initial focus; use if needed
	//document.test.inputbox1.focus ();
	return;

}

//-->

</script>
</head>
<body bgcolor="#FFFFFF" onLoad="loadDoc()">
<h3 align="center">Verificación de ingreso de datos en un formulario <br>
con JavaScript</h3>
<form NAME="test" ACTION="" METHOD="GET">
  <div align="center"><center><table border="0" cellspacing="0" cellpadding="0">
    <tr>
      <td><div align="left"><p><font face="Arial">I<small>ngresa tu e-mail :</small></font></td>
      <td><input TYPE="text" NAME="inputbox1" size="20"> </td>
      <td><input TYPE="button" NAME="1" VALUE="Test" onClick="runTest(this.form, this)"></td>
    </tr>
    <tr>
      <td><small><font face="Arial">Ingresa sólo 5 caracteres :</font></small></td>
      <td><input TYPE="text" NAME="inputbox2" size="20"></td>
      <td><input TYPE="button" NAME="2" VALUE="Test" onClick="runTest(this.form, this)"></td>
    </tr>
    <tr>
      <td><font face="arial" size="2">Ingresa 3 o más caracteres: </font></td>
      <td><input TYPE="text" NAME="inputbox3" size="20"></td>
      <td><input TYPE="button" NAME="3" VALUE="Test" onClick="runTest(this.form, this)"></td>
    </tr>
    <tr>
      <td><font face="arial" size="2">Ingresa cualquier cosa:</font> </td>
      <td><input TYPE="text" NAME="inputbox4" size="20"></td>
      <td><input TYPE="button" NAME="4" VALUE="Test" onClick="runTest(this.form, this)"></td>
    </tr>
    <tr>
      <td align="center"><input type="reset" name="reset" value="Inicializar"></td>
      <td align="center"><input TYPE="button" NAME="Submit" VALUE="Test final"
      onClick="runSubmit(this.form, this)"></td>
    </tr>
  </table>
  </center></div>
</form>
</body>
</html>
Ver ejemplo Javascript en funcionamiento